Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A power management method receives, from a meter that measures the amount
of surplus power, which is power supplied from a power generation
apparatus to a power system, a surplus power value indicating the amount
of surplus power, receives, from a first communication terminal used by a
user corresponding to first user identification information, an inquiry
about power supply in which the surplus power is used in a first time
period that lasts a certain unit time, the inquiry being associated with
the first user identification information, issues, in accordance with the
inquiry, first power identification information for validating power
supply performed by a power supply apparatus using the surplus power
corresponding to the first time period for an accumulated value of the
amount of surplus power corresponding to the first time period, transmits
the first power identification information and the accumulated value of
the amount of surplus power corresponding to the first time period to the
first communication terminal, and causes the power supply apparatus that
has received a first power supply request, which is associated with the
first power identification information, indicating that power is to be
supplied to the first load apparatus to supply an amount of first power
equal to or smaller than the amount of surplus power to the first load
apparatus as power that does not cause a charging process.

Claims:

1. A power management method used in a power management system including
a power generation apparatus corresponding to first user identification
information, a first load apparatus used by a user corresponding to the
first user identification information, and a power supply apparatus
capable of supplying power to the first load apparatus and installed in a
place different from a place where the power generation apparatus is
installed, the method comprising: receiving, from a meter that measures
amount of surplus power, which is, in power generated by the power
generation apparatus, power supplied from the power generation apparatus
to a power system, a surplus power value indicating the amount of surplus
power; receiving, from a first communication terminal used by the user
corresponding to the first user identification information, an inquiry
about power supply in which the surplus power is used in a first time
period that lasts a certain unit time, the inquiry being associated with
the first user identification information; issuing, in accordance with
the inquiry, first power identification information for validating power
supply performed by the power supply apparatus using the surplus power
corresponding to the first time period for an accumulated value of the
amount of surplus power corresponding to the first time period;
transmitting the first power identification information and the
accumulated value of the amount of surplus power corresponding to the
first time period to the first communication terminal; and causing the
power supply apparatus that has received a first power supply request,
which is associated with the first power identification information,
indicating that power is to be supplied to the first load apparatus to
supply an amount of first power equal to or smaller than the amount of
surplus power to the first load apparatus as power that does not cause a
charging process.

2. The method according to claim 1, wherein the first power supply
request is input from the first communication terminal to the power
supply apparatus.

3. The method according to claim 1, wherein the surplus power value is
periodically received from the meter, and wherein, after the inquiry is
received, surplus power values are accumulated from a start of the first
time period including a reception time, which is a time at which the
inquiry has been received, to the reception time to generate an
accumulated value of the amount of surplus power corresponding to the
first time period.

4. The method according to claim 1, wherein, after the inquiry is
received, the meter is requested to output surplus power values
corresponding to the first time period including a reception time, which
is a time at which the inquiry has been received, and wherein, after the
surplus power values corresponding to the first time period are received
from the meter, the surplus power values corresponding to the first time
period are accumulated to generate an accumulated value of the amount of
surplus power corresponding to the first time period.

5. The method according to claim 1, wherein the first power supply
request includes a value indicating amount of power to be supplied to the
first load apparatus.

6. The method according to claim 1, wherein, if the accumulated value of
the amount of surplus power corresponding to the first time period is
equal to or smaller than a certain minimum value, control is performed
such that the first power identification information is not issued or
associated with the accumulated value of the amount of surplus power
corresponding to the first time period.

7. The method according to claim 1, wherein, if the accumulated value of
the amount of surplus power corresponding to the first time period is
equal to or smaller than a certain minimum value, control is performed
such that the first power identification information and the accumulated
value are not transmitted to the first communication terminal in
accordance with the inquiry.

8. The method according to claim 1, wherein, if the accumulated value of
the amount of surplus power corresponding to the first time period is
equal to or smaller than a certain minimum value, control is performed
such that a notification indicating that the accumulated value of the
amount of surplus power corresponding to the first time period is equal
to or smaller than the certain minimum value is transmitted to the first
communication terminal in accordance with the inquiry.

9. The method according to claim 1, further comprising: receiving, from
the power supply apparatus, an inquiry request including a value
indicating amount of power to be supplied to the first load apparatus;
and outputting, if the value included in the inquiry request exceeds the
accumulated value of the amount of surplus power corresponding to the
first time period, an instruction to prohibit the power supply apparatus
from supplying power to the first load apparatus.

10. The method according to claim 1, further comprising: receiving, from
the power supply apparatus, an inquiry request including a value
indicating amount of power to be supplied to the first load apparatus;
and causing, if the value included in the inquiry request exceeds the
accumulated value of the amount of surplus power corresponding to the
first time period, the power generation apparatus to supply an amount of
first power corresponding to the accumulated value of the amount of
surplus power corresponding to the first time period to the first load
apparatus as power that does not cause a charging process.

11. The method according to claim 1, wherein, after the first time period
ends, management is performed such that power supply performed by the
power supply apparatus using the surplus power corresponding to the first
time period on the basis of the first power identification information is
invalidated.

12. The method according to claim 1, wherein the power management system
further includes a second load apparatus, which is different from the
first load apparatus and installed in the same building as the power
generation apparatus, and wherein power obtained by subtracting power
used by the second load apparatus from the power generated by the power
generation apparatus is determined as the surplus power.

13. The method according to claim 1, wherein, if the power generation
apparatus has not obtained the first power identification information,
the power supply apparatus supplies second power that causes a charging
process to the first load apparatus.

14. The method according to claim 13, wherein the power supply apparatus
includes a receiver used for a process for paying money for supplied
power, the method further comprising: performing control, if the second
power has been supplied, such that the receiver accepts the process for
paying money, and control, if the first power has been supplied, such
that the receiver prohibits the process for paying money.

15. The method according to claim 1, further comprising: performing a
process for calculating a price corresponding to the amount of surplus
power, wherein, if the power supply apparatus has supplied the first
power to the first load apparatus, a process for calculating a price
corresponding to amount of power obtained by subtracting amount of first
power supplied from the accumulated value of the amount of surplus power
is performed in the calculation process.

16. The method according to claim 1, wherein the first communication
terminal transmits the first power identification information and the
accumulated value of the amount of surplus power corresponding to the
first time period to a second communication terminal used by a user
corresponding to second user identification information different from
the first user identification information, and wherein, if the second
communication terminal has transmitted, to the power supply apparatus, a
second power supply request indicating that power is to be supplied to a
third load apparatus, which is used by the user corresponding to the
second user identification information and different from the first load
apparatus, the power supply apparatus supplies an amount of first power
equal to or smaller than the amount of surplus power to the third load
apparatus as power that does not cause a charging process.

17. The method according to claim 1, wherein the first power
identification information and temporary second power identification
information different from the first power identification information are
associated with the accumulated value of the amount of surplus power
corresponding to the first time period and issued in accordance with the
inquiry, wherein the first power identification information, the second
power identification information, and the accumulated value of the amount
of surplus power corresponding to the first time period are transmitted
to the first communication terminal, wherein the first communication
terminal transmits the second power identification information and the
accumulated value of the amount of surplus power to a second
communication terminal used by a user corresponding to second user
identification information different from the first user identification
information, wherein the second communication terminal transmits, to the
power supply apparatus, a second power supply request indicating that
power is to be supplied to a second load apparatus, which is used by the
user corresponding to the second user identification information and
different from the first load apparatus, and wherein, if the power supply
apparatus has supplied an amount of first power equal to or smaller than
the amount of surplus power to the second load apparatus as power that
does not cause a charging process, the first power is prohibited from
being supplied to the first load apparatus.

18. The method according to claim 1, wherein the accumulated value of the
amount of surplus power corresponding to the first time period includes a
value obtained by adding surplus power values corresponding to a period
from a start of the first time period including a reception time, which
is a time at which the inquiry has been received, to the reception time
to an estimated accumulated value of the amount of surplus power from the
reception time to an end of the first time period.

19. A power management system including a power generation apparatus
corresponding to first user identification information, a first load
apparatus used by a user corresponding to the first user identification
information, and a power supply apparatus capable of supplying power to
the first load apparatus and installed in a place different from the
power generation apparatus, the power management system comprising: one
or more memories; and circuitry operative to: receive, from a meter that
measures amount of surplus power, which is, in power generated by the
power generation apparatus, power supplied from the power generation
apparatus to a power system, a surplus power value indicating the amount
of surplus power; receive, from a first communication terminal used by
the user corresponding to the first user identification information, an
inquiry about power supply in which the surplus power is used in a first
time period that lasts a certain unit time, the inquiry being associated
with the first user identification information; issue, in accordance with
the inquiry, first power identification information for validating power
supply performed by the power supply apparatus using the surplus power
corresponding to the first time period for an accumulated value of the
amount of surplus power corresponding to the first time period; transmit
the first power identification information and the accumulated value of
the amount of surplus power corresponding to the first time period to the
first communication terminal; and cause the power supply apparatus that
has received, from the first communication terminal, a first power supply
request, which is associated with the first power identification
information, indicating that power is to be supplied to the first load
apparatus to supply an amount of first power equal to or smaller than the
amount of surplus power to the first load apparatus as power that does
not cause a charging process.

20. A power supply apparatus connected to the power management system
according to claim 19.

Description:

BACKGROUND

[0001] 1. Technical Field

[0002] The present disclosure relates to a power management method, a
power management system, and a power supply apparatus.

[0003] 2. Description of the Related Art

[0004] Power generated using solar energy and the like are currently
consumed by load apparatuses or supplied to a power system.

[0005] An apparatus that supplies power from a vehicle to power equipment
outside the vehicle using a storage battery mounted on the vehicle and
then supplies an amount of power corresponding to the amount of the
aforementioned power from the power equipment to the vehicle has been
disclosed (refer to Japanese Unexamined Patent Application Publication
No. 2013-102673).

SUMMARY

[0006] In the power management system in an example of the related art,
however, surplus power is always sold, and it is difficult for users to
make wider use of surplus power.

[0007] One non-limiting and exemplary embodiment provides a power
management method by which it is possible to make wider use of surplus
power.

[0008] In one general aspect, the techniques disclosed here feature a
power management method used in a power management system including a
power generation apparatus corresponding to first user identification
information, a first load apparatus used by a user corresponding to the
first user identification information, and a power supply apparatus
capable of supplying power to the first load apparatus and installed in a
place different from a place where the power generation apparatus is
installed. The method includes receiving, from a meter that measures
amount of surplus power, which is, in power generated by the power
generation apparatus, power supplied from the power generation apparatus
to a power system, a surplus power value indicating the amount of surplus
power, receiving, from a first communication terminal used by the user
corresponding to the first user identification information, an inquiry
about power supply in which the surplus power is used in a first time
period that lasts a certain unit time, the inquiry being associated with
the first user identification information, issuing, in accordance with
the inquiry, first power identification information for validating power
supply performed by the power supply apparatus using the surplus power
corresponding to the first time period for an accumulated value of the
amount of surplus power corresponding to the first time period,
transmitting the first power identification information and the
accumulated value of the amount of surplus power corresponding to the
first time period to the first communication terminal, and causing the
power supply apparatus that has received a first power supply request,
which is associated with the first power identification information,
indicating that power is to be supplied to the first load apparatus to
supply an amount of first power equal to or smaller than the amount of
surplus power to the first load apparatus as power that does not cause a
charging process.

[0009] The power management method in the present disclosure makes it
possible to make wider use of surplus power.

[0010] It should be noted that general or specific embodiments may be
implemented as a system, a method, an integrated circuit, a computer
program, a recording medium such as a computer-readable compact disc
read-only memory (CD-ROM), or any selective combination thereof.

[0011] Additional benefits and advantages of the disclosed embodiments
will become apparent from the specification and drawings. The benefits
and/or advantages may be individually obtained by the various embodiments
and features of the specification and drawings, which need not all be
provided in order to obtain one or more of such benefits and/or
advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is an overview of the configuration of a power management
system according to a first embodiment;

[0013] FIG. 2 is a block diagram illustrating the configuration of the
power management system according to the first embodiment;

[0014] FIG. 3 is a schematic diagram specifically illustrating a part of
the power management system according to the first embodiment including a
user's home;

[0015] FIG. 4 is a block diagram illustrating specific function blocks of
a power management apparatus according to the first embodiment;

[0016] FIG. 5 is a diagram illustrating a surplus power information table
according to the first embodiment;

[0017] FIG. 6 is a diagram illustrating a power identifier (ID) management
table according to the first embodiment;

[0018] FIG. 7 is a diagram illustrating a surplus power use information
table according to the first embodiment;

[0019] FIG. 8 is a diagram illustrating a power information management
table according to the first embodiment;

[0020] FIG. 9 is a diagram illustrating a power supply apparatus use
information table according to the first embodiment;

[0021] FIG. 10 is a diagram illustrating surplus power according to the
first embodiment;

[0022] FIG. 11 is a diagram illustrating an inquiry about the possibility
of power supply and a response to the inquiry according to the first
embodiment;

[0023] FIG. 12 is a flowchart illustrating an overall process performed by
the power management system according to the first embodiment;

[0024] FIG. 13 is a sequence diagram illustrating transmission of
information in the power management system according to the first
embodiment from a process for inquiring about the possibility of power
supply to a process for reporting power supply;

[0025] FIG. 14 is a sequence diagram illustrating transmission of
information in the power management system according to a modification of
the first embodiment from the process for inquiring about the possibility
of power supply to the process for reporting power supply;

[0026] FIG. 15 is a sequence diagram illustrating transmission of
information in the power management system according to the first
embodiment during a charging process;

[0027] FIG. 16 is a flowchart illustrating a process performed by the
power management apparatus according to the first embodiment;

[0028] FIG. 17 is a first flowchart illustrating a process for identifying
surplus power performed by a surplus power identification unit according
to the first embodiment;

[0029] FIG. 18 is a second flowchart illustrating the process for
identifying surplus power performed by the power management apparatus
according to the first embodiment;

[0030] FIG. 19 is a flowchart illustrating a process for inquiring about a
power ID performed by the power management apparatus according to the
first embodiment;

[0031] FIG. 20 is a flowchart illustrating a process for updating the
amount of surplus power used performed by the power management apparatus
according to the first embodiment;

[0032] FIG. 21 is a flowchart illustrating a process for calculating an
electricity bill in a settlement process according to the first
embodiment;

[0033] FIG. 22 is an overview of the configuration of a power management
system according to a second embodiment;

[0034] FIG. 23 is a block diagram illustrating the configuration of the
power management system according to the second embodiment;

[0035] FIG. 24 is a first sequence diagram illustrating transmission of
information in the power management system according to the second
embodiment;

[0036] FIG. 25 is a first sequence diagram illustrating transmission of
information in a power management system according to a third embodiment;

[0037] FIG. 26 is a second sequence diagram illustrating the transmission
of information in the power management system according to the third
embodiment;

[0038] FIG. 27 is a third sequence diagram illustrating the transmission
of information in the power management system according to the third
embodiment;

[0039] FIG. 28 is a block diagram illustrating another example of the
configuration of the power management system according to each
embodiment; and

[0040] FIG. 29 is a flowchart illustrating a power management method in
the power management system according to each embodiment.

DETAILED DESCRIPTION

Underlying Knowledge Forming Basis of the Present Disclosure

[0041] The present inventor has found that the following problem occurs in
the transmission of power described in "Description of the Related Art".

[0042] After the power liberalization in Japan in 2016, consumers will be
able to select any power retailers. Because regulations on electricity
bills will be removed, retailers need to propose attractive contracts or
rate plans that are useful to consumers.

[0043] Retailers will make contracts not only with conventional power
supply points (households and buildings) but also with individuals. In
addition, a contract will be possible that specifies that if a consumer
receives power with a device (a mobile device, an electric vehicle (EV),
or the like) at a place other than the consumer's home (e.g., a public
charging spot), the consumer pays for the power with a single transaction
along with power consumed in the consumer's home.

[0044] On the other hand, power generated by consumers using renewable
energy such as solar energy is now purchased by power companies for
premium prices in order to tactically popularize such a type of power
generation. As solar power generation equipment becomes popular, however,
the prices are falling. In the future, the prices can be equal to or
lower than those of grid power.

[0045] In such a situation, consumers might not sell surplus power caused
by home solar power systems to power companies but might want to use the
surplus power themselves or provide (or present) the surplus power for
others such as friends or relatives.

[0046] In the power management system in the example of the related art,
however, surplus power is always sold, and it is difficult for users to
make wider use of surplus power.

[0047] The present disclosure provides a power management system capable
of making wider use of surplus power.

[0048] In order to solve such a problem, a power management method
according to an aspect of the present disclosure is a power management
method used in a power management system including a power generation
apparatus corresponding to first user identification information, a first
load apparatus used by a user corresponding to the first user
identification information, and a power supply apparatus capable of
supplying power to the first load apparatus and installed in a place
different from a place where the power generation apparatus is installed.
The method includes receiving, from a meter that measures amount of
surplus power, which is, in power generated by the power generation
apparatus, power supplied from the power generation apparatus to a power
system, a surplus power value indicating the amount of surplus power,
receiving, from a first communication terminal used by the user
corresponding to the first user identification information, an inquiry
about power supply in which the surplus power is used in a first time
period that lasts a certain unit time, the inquiry being associated with
the first user identification information, issuing, in accordance with
the inquiry, first power identification information for validating power
supply performed by the power supply apparatus using the surplus power
corresponding to the first time period for an accumulated value of the
amount of surplus power corresponding to the first time period,
transmitting the first power identification information and the
accumulated value of the amount of surplus power corresponding to the
first time period to the first communication terminal, and causing the
power supply apparatus that has received a first power supply request,
which is associated with the first power identification information,
indicating that power is to be supplied to the first load apparatus to
supply an amount of first power equal to or smaller than the amount of
surplus power to the first load apparatus as power that does not cause a
charging process.

[0049] According to the above aspect, in the power management system, the
surplus power caused in a home of a user (consumer) is supplied to the
power system (reverse flow) whereas the power system supplies power at a
place different from the user's home. As a result, the user can not only
sell the surplus power but also receive an amount of power corresponding
to the amount of surplus power at another place. The power management
system can thus make wider use of surplus power. In other words, since
the user consumes the surplus power at a place different from his/her
home, the power management system can balance the amount of power
consumed and the amount of power supplied with each other more
appropriately in the first time period.

[0050] The first power supply request may be, for example, input from the
first communication terminal to the power supply apparatus.

[0051] According to the above aspect, in the power management system, the
power supply apparatus receives the first power supply request from the
first communication terminal. The power management system can therefore
receive the first power supply request more securely using the first
communication terminal.

[0052] The surplus power value may be, for example, periodically received
from the meter. After the inquiry is received, surplus power values may
be accumulated from a start of the first time period including a
reception time, which is a time at which the inquiry has been received,
to the reception time to generate an accumulated value of the amount of
surplus power corresponding to the first time period.

[0053] According to the above aspect, in the power management system, the
accumulated value of the amount of surplus power can be specifically
calculated using the surplus power value periodically transmitted from
the meter.

[0054] After the inquiry is received, for example, the meter may be
requested to output surplus power values corresponding to the first time
period including a reception time, which is a time at which the inquiry
has been received. After the surplus power values corresponding to the
first time period are received from the meter, the surplus power values
corresponding to the first time period may be accumulated to generate an
accumulated value of the amount of surplus power corresponding to the
first time period.

[0055] According to the above aspect, in the power management system, the
accumulated value of the amount of surplus power can be specifically
calculated using the surplus power value periodically transmitted from
the meter.

[0056] The first power supply request may include, for example, a value
indicating amount of power to be supplied to the first load apparatus.

[0057] According to the above aspect, since the power management apparatus
receives the power supply request including the amount of power to be
supplied in the power management system, the power management apparatus
can determine whether an amount of power corresponding the amount of
power included in the power supply request can be supplied.

[0058] If the accumulated value of the amount of surplus power
corresponding to the first time period is equal to or smaller than a
certain minimum value, for example, control may be performed such that
the first power identification information is not issued or associated
with the accumulated value of the amount of surplus power corresponding
to the first time period.

[0059] According to the above aspect, if the amount of power that can be
supplied from the power supply apparatus is equal to or smaller than the
certain minimum value, the power management apparatus can prohibit the
power supply apparatus from supply power by controlling the issuance of
the power ID.

[0060] If the accumulated value of the amount of surplus power
corresponding to the first time period is equal to or smaller than a
certain minimum value, for example, control may be performed such that
the first power identification information and the accumulated value are
not transmitted to the first communication terminal in accordance with
the inquiry.

[0061] According to the above aspect, if the amount of power that can be
supplied from the power supply apparatus is equal to or smaller than the
certain minimum value, the power management apparatus can prohibit the
power supply apparatus from supplying power by controlling the issuance
of the power ID.

[0062] If the accumulated value of the amount of surplus power
corresponding to the first time period is equal to or smaller than a
certain minimum value, for example, control may be performed such that a
notification indicating that the accumulated value of the amount of
surplus power corresponding to the first time period is equal to or
smaller than the certain minimum value is transmitted to the first
communication terminal in accordance with the inquiry.

[0063] According to the above aspect, the power management apparatus can
notify the user that the amount of power that can be supplied from the
power supply apparatus is equal to or smaller than the certain minimum
value by transmitting the notification to the first communication
terminal.

[0064] The method further may include, for example, receiving, from the
power supply apparatus, an inquiry request including a value indicating
amount of power to be supplied to the first load apparatus, and
outputting, if the value included in the inquiry request exceeds the
accumulated value of the amount of surplus power corresponding to the
first time period, an instruction to prohibit the power supply apparatus
from supplying power to the first load apparatus.

[0065] According to the above aspect, the power management apparatus can
prohibit the power supply apparatus from supplying power using the
instruction to prohibit the power supply apparatus from supplying an
amount of power larger than the amount of surplus power.

[0066] The method further may include, for example, receiving, from the
power supply apparatus, an inquiry request including a value indicating
amount of power to be supplied to the first load apparatus, and causing,
if the value included in the inquiry request exceeds the accumulated
value of the amount of surplus power corresponding to the first time
period, the power generation apparatus to supply an amount of first power
corresponding to the accumulated value of the amount of surplus power
corresponding to the first time period to the first load apparatus as
power that does not cause a charging process.

[0067] According to the above aspect, the power management apparatus can
supply an amount of power equal to or smaller than the amount of surplus
power in response to the request to supply an amount of power larger than
the amount of surplus power.

[0068] After the first time period ends, for example, management may be
performed such that power supply performed by the power supply apparatus
using the surplus power corresponding to the first time period on the
basis of the first power identification information is invalidated.

[0069] According to the above aspect, the power management system can
perform power supply based on the first identification information only
in the first time period. The power management system can therefore make
wider use of surplus power without significantly disrupting power
supply-demand balance in a transmission and distribution network.

[0070] The power management system further may include, for example, a
second load apparatus, which is different from the first load apparatus
and installed in the same building as the power generation apparatus.
Power obtained by subtracting power used by the second load apparatus
from the power generated by the power generation apparatus is determined
as the surplus power.

[0071] According to the above aspect, the power management apparatus can
specifically calculate the amount of surplus power using the amount of
power generated by the power generation apparatus and the amount of power
consumed by the second load apparatus.

[0072] If the power generation apparatus has not obtained the first power
identification information, for example, the power supply apparatus may
supply second power that causes a charging process to the first load
apparatus.

[0073] According to the above aspect, in the power management system, the
power supply apparatus can supply either power that causes a charging
process or power that does not cause a charging process on the basis of
whether the first power identification information is present. Since the
power management system performs management such that the surplus power
offsets the power supplied from the power supply apparatus, the user need
not pay for the power supplied from the power supply apparatus. The user
can therefore make wider use of surplus power without paying extra money.

[0074] The power supply apparatus may include, for example, a receiver
used for a process for paying money for supplied power. The method may
further include performing control, if the second power has been
supplied, such that the receiver accepts the process for paying money,
and control, if the first power has been supplied, such that the receiver
prohibits the process for paying money.

[0075] According to the above aspect, the power management system
determines whether to accept the process for paying money in accordance
with whether the supplied power causes a charging process. The power
management system can therefore appropriately perform the process for
paying money for the supplied power.

[0076] The method further may include, for example, performing a process
for calculating a price corresponding to the amount of surplus power. If
the power supply apparatus has supplied the first power to the first load
apparatus, a process for calculating a price corresponding to amount of
power obtained by subtracting amount of first power supplied from the
accumulated value of the amount of surplus power may be performed in the
calculation process.

[0077] According to the above aspect, the power management system
provides, for the user, the price corresponding to the amount of power
obtained by subtracting the amount of power supplied from the power
supply apparatus from the price corresponding to the amount of surplus
power. The user can therefore make wider use of surplus power without
paying extra money.

[0078] The first communication terminal may transmit, for example, the
first power identification information and the accumulated value of the
amount of surplus power corresponding to the first time period to a
second communication terminal used by a user corresponding to second user
identification information different from the first user identification
information. If the second communication terminal has transmitted, to the
power supply apparatus, a second power supply request indicating that
power is to be supplied to a third load apparatus, which is used by the
user corresponding to the second user identification information and
different from the first load apparatus, the power supply apparatus may
supply an amount of first power equal to or smaller than the amount of
surplus power to the third load apparatus as power that does not cause a
charging process.

[0079] According to the above aspect, in the power management system, the
surplus power caused in a home of a first user (the user corresponding to
the first user identification information) is supplied to the power
system (reverse flow) whereas a second user (the user corresponding to
the second user identification information) that does not own a power
generation apparatus can receive power from the power system. Even users
who do not own a power generation apparatus can therefore use surplus
power.

[0080] The first power identification information and temporary second
power identification information different from the first power
identification information may be, for example, associated with the
accumulated value of the amount of surplus power corresponding to the
first time period and issued in accordance with the inquiry. The first
power identification information, the second power identification
information, and the accumulated value of the amount of surplus power
corresponding to the first time period may be transmitted to the first
communication terminal. The first communication terminal may transmit the
second power identification information and the accumulated value of the
amount of surplus power to a second communication terminal used by a user
corresponding to second user identification information different from
the first user identification information. The second communication
terminal may transmit, to the power supply apparatus, a second power
supply request indicating that power is to be supplied to a second load
apparatus, which is used by the user corresponding to the second user
identification information and different from the first load apparatus.
If the power supply apparatus has supplied an amount of first power equal
to or smaller than the amount of surplus power to the second load
apparatus as power that does not cause a charging process, the first
power may be prohibited from being supplied to the first load apparatus.

[0081] According to the above aspect, in the power management system, the
second user is allowed to supply power to his/her load apparatus using
the second identification information whereas the first user is
prohibited from supplying power to his/her load apparatus. That is, the
power management system can appropriately transfer or move identification
information from the first user to the second user.

[0082] The accumulated value of the amount of surplus power corresponding
to the first time period may include, for example, a value obtained by
adding surplus power values corresponding to a period from a start of the
first time period including a reception time, which is a time at which
the inquiry has been received, to the reception time to an estimated
accumulated value of the amount of surplus power from the reception time
to an end of the first time period.

[0083] According to the above aspect, in the power management system, the
sum of the surplus power actually caused in the time period and the
surplus power estimated to be caused in the time period can be supplied
to the load apparatus. As a result, it is possible to avoid increasing a
power procurement cost of a retailer.

[0084] A power management system according to an aspect of the present
disclosure is a power management system including a power generation
apparatus corresponding to first user identification information, a first
load apparatus used by a user corresponding to the first user
identification information, and a power supply apparatus capable of
supplying power to the first load apparatus and installed in a place
different from the power generation apparatus. The power management
system including one or more memories; and circuitry operative to:
receive, from a meter that measures amount of surplus power, which is, in
power generated by the power generation apparatus, power supplied from
the power generation apparatus to a power system, a surplus power value
indicating the amount of surplus power, receive, from a first
communication terminal used by the user corresponding to the first user
identification information, an inquiry about power supply in which the
surplus power is used in a first time period that lasts a certain unit
time, the inquiry being associated with the first user identification
information, issue, in accordance with the inquiry, first power
identification information for validating power supply performed by the
power supply apparatus using the surplus power corresponding to the first
time period for an accumulated value of the amount of surplus power
corresponding to the first time period, transmit the first power
identification information and the accumulated value of the amount of
surplus power corresponding to the first time period to the first
communication terminal, and cause the power supply apparatus that has
received, from the first communication terminal, a first power supply
request, which is associated with the first power identification
information, indicating that power is to be supplied to the first load
apparatus to supply an amount of first power equal to or smaller than the
amount of surplus power to the first load apparatus as power that does
not cause a charging process.

[0085] According to the above aspect, the same advantageous effects as
those produced by the power management method can be produced.

[0086] A power supply apparatus according to an aspect of the present
disclosure is a power supply apparatus connected to the power management
system.

[0087] According to the above aspect, the same advantageous effects as
those produced by the power management method can be produced.

[0088] It should be noted that general or specific embodiments may be
implemented as a system, a method, an integrated circuit, a computer
program, a storage medium such as a CD-ROM, or any selective combination
thereof.

[0089] Embodiments will be specifically described hereinafter with
reference to the drawings.

[0090] It should be noted that the following embodiments are general or
specific examples. Values, shapes, materials, components, positions at
which the components are arranged, how the components are connected to
one another, steps, the order of steps, and the like are examples, and do
not limit the present disclosure. Components in the following description
that are not described in the independent claims, which define broadest
concepts, are described as arbitrary components.

First Embodiment

[0091] In a first embodiment, a power management system will be described
capable of making wider use of surplus power caused in a user's home by
consuming the surplus power at a place different from the user's home.

[0092] First, a situation in which the power management system according
to the present embodiment manages power will be described using an
example. Power management performed by the power management system
according to the present embodiment, however, is not limited to this
example.

[0093] The user drives an EV to go to a supermarket and charges the EV
during shopping. A power supply apparatus for charging EVs is installed
in a parking lot of the supermarket, and the user charges the EV using
the power supply apparatus. A power generation apparatus is installed in
the user's home and generating power. While the user is charging the EV,
surplus power is caused in the user's home because the amount of power
consumed by a load apparatus in the user's home is smaller than the
amount of power generated. The power management system performs
management such that the surplus power caused in the user's home offsets
the power supplied to the EV from the power supply apparatus. The power
management system that performs such power management will be
specifically described hereinafter.

[0094] FIG. 1 is an overview of the configuration of a power management
system 1 according to the present embodiment. FIG. 2 is a block diagram
illustrating the configuration of the power management system 1 according
to the present embodiment. In FIG. 1 and other drawings, solid lines
indicate transmission of power, and broken lines indicate transmission of
information or control. The power management system 1 will be described
with reference to these drawings.

[0095] As illustrated in FIGS. 1 and 2, the power management system 1
according to the present embodiment includes a power supply apparatus 10,
a home 20 of a user U1, a retailer 40, and a transmission and
distribution network 50.

[0096] The power supply apparatus 10 is connected to the transmission and
distribution network 50 and supplies power supplied from the transmission
and distribution network 50 to a load apparatus 32. The power supply
apparatus 10 holds a power ID of surplus power and supplies an amount of
power (also referred to as "first power") equal to or smaller than the
amount of the surplus power associated with the held power ID to the load
apparatus 32 from the transmission and distribution network 50.

[0097] The power supply apparatus 10 includes an input interface 11 and a
power supply unit 12.

[0098] The input interface 11 is a user interface that receives an
operation performed by the user U1 or information. The input interface 11
may be a near field communication port that communicates information with
a communication terminal 31 through near field communication or the like,
or may be keys or buttons that receive an operation performed by the user
U1 when pressed.

[0099] The power supply unit 12 is a power output unit that supplies power
supplied from the transmission and distribution network 50 to the load
apparatus 32. The power supply unit 12 supplies power to the load
apparatus 32 connected to the power supply unit 12 on the basis of
control performed by a power management apparatus 41. More specifically,
the power supply unit 12 supplies an amount of power specified by the
power management apparatus 41 to the load apparatus 32.

[0100] Even if the power management apparatus 41 does not specify an
amount of power, the power supply unit 12 supplies an amount of power
(also referred to as "second power") separately specified by the user U1
or another person to the load apparatus 32. A charging process performed
by the power management apparatus 41 after the power supply unit 12
supplies the second power, however, is different from a charging process
performed after the first power is supplied.

[0101] A control unit 13 is a processing unit that controls the operation
of the power supply apparatus 10 on the basis of information obtained
from the input interface 11 or the like. The control unit 13 supplies
power to the load apparatus 32 in accordance with a power supply request
received from the communication terminal 31 through the input interface
11. More specifically, if a power ID included in a power supply request
is input, the control unit 13 inquires about the power ID included in the
power supply request and supplies an amount of power smaller than the
amount of surplus power associated with the power ID to the load
apparatus 32 from the power supply unit 12.

[0102] The power ID used is not limited to one included in a power supply
request. The power ID used may be one obtained by another method, or may
be one generated by the control unit 13 itself, instead. That is, the
control unit 13 may inquire about a power ID held thereby and supply an
amount of power smaller than the amount of surplus power associated with
the power ID to the load apparatus 32 from the power supply unit 12.

[0103] A power generation apparatus 21, a load apparatus 22, and a meter
23 are installed in the home 20 of the user U1.

[0104] The power generation apparatus 21 generates power and outputs the
generated power to the outside. The power generation apparatus 21
supplies surplus power, which is power generated thereby except for power
consumed by the load apparatus 22, that is, power obtained by subtracting
the power consumed by the load apparatus 22 from the power generated
thereby, to the transmission and distribution network 50 (reverse flow).
The power generation apparatus 21 is realized, for example, by a solar
panel or a fuel cell. The power generation apparatus 21 includes a device
(e.g., a power conditioner) that converts power obtained from a solar
panel, a fuel cell, or the like into power that can be supplied to the
load apparatus 22 or the like. The power generation apparatus 21
corresponds to a power generation apparatus corresponding to first user
identification information.

[0105] The load apparatus 22 is an apparatus that consumes power, that is,
for example, a home appliance or an EV. The load apparatus 22 may be a
storage battery, instead. The load apparatus 22 corresponds to a second
load apparatus.

[0106] As illustrated in FIG. 2, the meter 23 is mounted on a power line
and measures the amount of power that flows therethrough. The meter 23
measures the amount of surplus power (the so-called amount of power sold)
supplied to the transmission and distribution network 50 from the home 20
of the user U1 in each measurement period and transmits the amount of
power measured to the power management apparatus 41. The measurement
period herein refers to a period of a predetermined length in which the
meter 23 keeps measuring the amount of power. Although an example in
which the length of the measurement period is 5 minutes will be described
hereinafter, the length of the measurement period is not limited to this.
The length of the measurement period may be arbitrarily determined
insofar as the length is shorter than the length of a time period
(described later). The length of the measurement may be, for example, 1
minute or 10 minutes. If the power management apparatus 41 inquires of
the meter 23 about the amount of power in a certain period in the past or
present, the meter 23 transmits a value indicating the amount of power in
the certain period in response to the inquiry.

[0107] The user U1 stays near the power supply apparatus 10 installed in a
place different from the home 20. The user U1 owns the communication
terminal 31 and the load apparatus 32.

[0108] The communication terminal 31 communicates with the power supply
apparatus 10 and the power management apparatus 41 on the basis of
operations performed by the user U1. More specifically, the communication
terminal 31 communicates with the power management apparatus 41 to
inquire about the possibility of power supply and obtain a power ID
necessary to supply power from the power supply apparatus 10. The
communication terminal 31 communicates with the power supply apparatus 10
to transmit the power ID to the power supply apparatus 10 and supply
power to the load apparatus 32 from the power supply apparatus 10. The
communication terminal 31 is, for example, a smartphone, a mobile phone
terminal, a personal computer (PC), or the like.

[0109] The load apparatus 32 is an electric device owned or carried by the
user U1. The load apparatus 32 receives power from the power supply
apparatus 10 if the communication terminal 31 transmits a power ID to the
power supply apparatus 10. The load apparatus 32 is, for example, a
mobile terminal, an EV, or the like. The load apparatus 32 may be the
communication terminal 31, instead. The load apparatus 32 may be any
electric device used by the user U1, and it does not matter whether the
user U1 has the ownership of the electric device. The load apparatus 32
corresponds to a first load apparatus.

[0110] The retailer 40 is a power retailer that makes money by supplying
power to consumers. The retailer 40 makes a power supply contract with
the user U1 using the power management apparatus 41 and charges the user
U1 a price corresponding to the amount of power used by the load
apparatus 22 in the home 20 of the user U1 and the amount of power used
by the load apparatus 32 through the power supply apparatus 10.

[0111] The power management apparatus 41 obtains the amount of surplus
power supplied in a certain period from the meter 23 of the home 20 of
the user U1 in accordance with an inquiry from the communication terminal
31 about the possibility of power supply in order to identify surplus
power caused in the certain period. The power management apparatus 41
then generates a power ID for uniquely identifying the identified surplus
power and transmits the generated power ID to the communication terminal
31. The power management apparatus 41 may periodically obtain the amount
of surplus power from the meter 23 of the home 20 of the user U1,
instead.

[0112] The power ID is not only a value indicating the amount of power but
also information associated with power identified by a place from which
the power is supplied, a period in which the power is supplied, the
amount of power, and the like. More specifically, the power ID generated
as above may be information associated with the amount of power supplied
from the home 20 of the user U1 in the certain period, the information
being identified by the meter 23. The power ID corresponds to first
identification information. A method for identifying surplus power will
be described in detail later.

[0113] The power management apparatus 41 performs a process for charging
the user U1 the price of power consumed by the user U1. More
specifically, the power management apparatus 41 performs a process for
charging the user U1 the price of power consumed in the home 20 of the
user U1. As a rule, if the power supply apparatus 10 has supplied power
to the load apparatus 32 of the user U1, the power management apparatus
41 performs a process for charging the user U1 the price of the supplied
power. As an exception, however, if the power supply apparatus 10 has
supplied power (first power) after holding a power ID, the power
management apparatus 41 does not perform a process for charging the user
U1 the price of the supplied power, that is, prohibits the charging
process. In the power supplied to the load apparatus 32 from the power
supply apparatus 10, the first power is power that does not cause a
charging process. Power other than the first power is the second power.
That is, if the power supply apparatus 10 has supplied power (second
power) to the load apparatus 32 of the user U1 without holding a power
ID, the power management apparatus 41 performs a process for charging the
user U1 the price of the supplied power. The second power is power that
causes a charging process.

[0114] The power management apparatus 41 (more specifically, a settlement
process unit 427, which will be described later) performs a process for
paying the user U1 money corresponding to the amount of surplus power
supplied from the home 20 of the user U1. If the first power has been
supplied to the load apparatus 32, the power management apparatus 41
performs a process for paying the user U1 money corresponding to the
amount of power obtained by subtracting the amount of the first power
from the amount of surplus power.

[0115] The transmission and distribution network 50 is connected to a
power system of a power company or a part of the power system. The
transmission and distribution network 50 is a network that distributes
grid power. The transmission and distribution network 50 supplies power
to the home 20 of the user U1 and the power supply apparatus 10.

[0116] The power supply apparatus 10 may further include a reception unit
(not illustrated) that receives money corresponding to the amount of
power supplied. If the power supply apparatus 10 has supplied power to
the load apparatus 32 of the user U1 and the power management apparatus
41 does not perform a charging process, the reception unit receives, from
the user U1, money corresponding to the amount of power supplied. As an
exception, however, if the power supply apparatus 10 has supplied the
first power, the reception unit does not receive, from the user U1, money
corresponding to the amount of power supplied, that is, prohibits the
reception of the money.

[0117] The reception unit is a slot into which bills and coins can be
thrown, a combination of a card slot that reads information from a card
having a settlement function and a communication unit, or a communication
unit that reads information from the communication terminal 31 having a
settlement function. The reception unit, however, is not limited to these
examples.

[0118] In the power management system 1, power supply-demand balance is
adjusted in each time period, which is a unit time in which the
supply-demand balance is adjusted. The power supply apparatus 10 may
supply the first power in the same time period in which the power
generation apparatus 21 supplies surplus power to the transmission and
distribution network 50. In doing so, the power management system 1 can
supply power to the load apparatus 32 without disrupting the power
supply-demand balance in the time period. As a result, it is possible to
avoid increasing a power procurement cost.

[0119] FIG. 3 is a schematic diagram specifically illustrating a part of
the power management system 1 according to the present embodiment
including the home 20 of the user U1.

[0120] As illustrated in FIG. 3, the home 20 of the user U1 is connected
to the transmission and distribution network 50, and other houses 20A and
20B are also connected to the transmission and distribution network 50.
The houses 20A and 20B may be houses having the same functions as the
home 20 of the user U1, or may be conventional houses that do not include
power generation equipment or the like.

[0121] As described above, the power generation apparatus 21, the load
apparatus 22, and the meter 23 are installed in the home 20 of the user
U1. An electric switchboard 24 and a meter 25 may also be installed in
the home 20 of the user U1.

[0122] The electric switchboard 24 is connected to the transmission and
distribution network 50, the power generation apparatus 21, and the load
apparatus 22. If the amount of power generated by the power generation
apparatus 21 exceeds the amount of power consumed by the load apparatus
22, the electric switchboard 24 supplies power to the transmission and
distribution network 50. If the amount of power generated by the power
generation apparatus 21 falls below the amount of power consumed by the
load apparatus 22, the electric switchboard 24 receives power from the
transmission and distribution network 50.

[0123] The meter 25 is a measuring device that is mounted on a power line
and that measures the amount of power that flows therethrough. The meter
25 measures the amount of power (the so-called amount of power purchased)
flowing from the transmission and distribution network 50 to the home 20
of the user U1 in each measurement period and transmits a value
indicating the measured amount of power to the power management apparatus
41.

[0124] Next, the power management apparatus 41 will be described in
detail.

[0125] FIG. 4 is a block diagram illustrating specific function blocks of
the power management apparatus 41 according to the present embodiment.

[0126] As illustrated in FIG. 4, the power management apparatus 41
includes a power information obtaining unit 421, a surplus power
identification unit 422, a communication unit 423, a power ID management
unit 424, a power supply possibility determination unit 425, a surplus
power use history management unit 426, and the settlement process unit
427.

[0127] The power information obtaining unit 421 is a processing unit that
obtains the amount of power sold in each time period, that is, the amount
of surplus power, from the meter 23. The power information obtaining unit
421 can also obtain the amount of power purchased in each time period
from the meter 25. The power information obtaining unit 421 then
associates the amount of power sold and the amount of power purchased
with the power supply contract and stores the amount of power sold, the
amount of power purchased, and the power supply contract in a power
information management table. The power information obtaining unit 421
also associates the amount of surplus power with the power supply
contract and stores the amount of surplus power and the power supply
contract in a surplus power information table.

[0128] The surplus power identification unit 422 is a processing unit that
receives an inquiry about the possibility of power supply from the
communication terminal 31 and that identifies surplus power in a time
period on the basis of the amount of surplus power in each measurement
period obtained by the power information obtaining unit 421.

[0129] More specifically, the surplus power identification unit 422
receives an inquiry about the possibility of power supply from the
communication terminal 31 through the communication unit 423. Upon
receiving the inquiry about the possibility of power supply, the surplus
power identification unit 422 identifies an accumulated value of the
amount of surplus power in each measurement period obtained by the power
information obtaining unit 421 as the amount of surplus power in the time
period. Alternatively, the surplus power identification unit 422 may
identify the amount of surplus power in the time period by adding an
estimated value of the amount of surplus power that has not been obtained
to the accumulated value of the amount of surplus power in each
measurement period obtained by the power information obtaining unit 421.

[0130] The communication unit 423 is a communication interface for
enabling the function blocks of the power management apparatus 41 to
communicate with the communication terminal 31.

[0131] The power ID management unit 424 is a processing unit that issues a
power ID and that associates the power ID with an accumulated value of
the amount of surplus power identified by the surplus power
identification unit 422. The power ID management unit 424 transmits the
identified amount of surplus power to the communication terminal 31
through the communication unit 423. The power ID management unit 424
associates the amount of surplus power and the power ID with each other
and stores the amount of surplus power and the power ID in a power ID
management table. Each power ID may be provided with an expiration time.
As the expiration time, an end time of a time period including a time at
which each power ID has been issued is used. The power ID management unit
424 can then manage power IDs whose expiration times have not yet come as
valid power IDs and power IDs whose expiration times have come as invalid
power IDs. If a power ID indicated in a record is valid, the power ID can
be used, that is, more specifically, the power supply apparatus 10 can
supply power using the power ID. If a power ID indicated in a record is
invalid, the power ID is not valid. In this case, the power ID cannot be
used, that is, the power supply apparatus 10 cannot supply power using
the power ID.

[0132] The power supply possibility determination unit 425 is a processing
unit that determines whether the amount of power indicated in a power
supply request received from the power supply apparatus 10 can be
supplied.

[0133] The surplus power use history management unit 426 is a processing
unit that receives a power supply report after the power supply apparatus
10 supplies power and that updates surplus power use information. The
surplus power use history management unit 426 associates a power ID and
the amount of power supplied using the power ID with each other and
stores the power ID and the amount of power in a surplus power use
information table. The surplus power use history management unit 426
associates a contract ID and the amount of power supplied from the power
supply apparatus 10 using the contract ID with each other and stores the
contract ID and the amount of power in a power supply apparatus use
information table.

[0134] The settlement process unit 427 is a processing unit that performs
a process for settling an electricity bill on the basis of the amount of
power purchased and the amount of power sold in the home 20 of the user
U1. The settlement process unit 427 performs the process for settling an
electricity bill in consideration of power supplied from the power supply
apparatus 10.

[0135] FIG. 5 is a diagram illustrating a surplus power information table
T10 according to the present embodiment.

[0136] The surplus power information table T10 is a table held by the
power information obtaining unit 421. In the surplus power information
table T10, the amount of surplus power in each measurement period
obtained by the power information obtaining unit 421 from the meter 23 is
stored as a record. Items of the surplus power information table T10 will
be described hereinafter.

[0137] "Contract ID" is an ID for uniquely identifying a power supply
contract in which the amount of surplus power indicated in a
corresponding record has been caused.

[0138] "Meter ID" is an ID for uniquely identifying the meter 23 that has
measured the amount of surplus power indicated in the corresponding
record.

[0139] "Measurement period start time" is a start time of a measurement
period in which the amount of surplus power indicated in the
corresponding record has been caused.

[0140] "Measurement period end time" is an end time of the measurement
period in which the amount of surplus power indicated in the
corresponding record has been caused.

[0141] "Amount of surplus power" is the amount of surplus power indicated
in the corresponding record and expressed, for example, in Wh.

[0142] A first record in the surplus power information table T10
illustrated in FIG. 5, for example, indicates that, in a power supply
contract whose contract ID is "00001", a meter 23 whose meter ID is
"123456789" has measured a surplus power of 340 Wh in a measurement
period "04/01/2015 10:30:00 to 10:35:00".

[0143] FIG. 6 is a diagram illustrating a power ID management table T20
according to the present embodiment.

[0144] The power ID management table T20 is a table held by the power ID
management unit 424. In the power ID management table T20, a power ID
issued by the power ID management unit 424 and associated with the amount
of surplus power is stored as a record. Items of the power ID management
table T20 will be described hereinafter.

[0145] "Power ID" is a power ID indicated in a corresponding record.

[0146] "Expiration time" is an expiration time of the power ID indicated
in the corresponding record, that is, at time at which the power ID
expires.

[0147] "Amount of surplus power" is the amount of surplus power associated
with the power ID indicated in the corresponding record, that is, the
amount of surplus power associated when the power ID has been issued.

[0148] "Amount of power available" is the amount of power available in the
amount of surplus power associated with the power ID indicated in the
corresponding record. The amount of power available is the same as the
amount of surplus power immediately after the power ID issued, but
decreases as the surplus power is consumed.

[0149] "Record registration time" is a time at which the corresponding
record has been registered.

[0150] A first record in the power ID management table T20 illustrated in
FIG. 6, for example, indicates that a power ID "1504011040766" is
associated with a surplus power of 766 Wh and a power of 766 Wh is
available. The expiration time of the power ID is "04/01/2015 11:00:00",
and the time at which the record has been registered is "04/01/2015
10:40:00".

[0151] FIG. 7 is a diagram illustrating a surplus power use information
table T30 according to the present embodiment.

[0152] The surplus power use information table T30 is a table held by the
surplus power use history management unit 426. In the surplus power use
information table T30, the amount of power used by the power supply
apparatus 10 for supplying power is stored as a record.

[0153] "Power ID" is a power ID associated with the amount of power used
for power supply indicated in a corresponding record.

[0154] "Power supply start time" is a time at which the power supply
apparatus 10 indicated in the corresponding record has started supplying
power.

[0155] "Power supply end time" is a time at which the power supply
apparatus 10 indicated in the corresponding record has stopped supplying
power.

[0156] "Amount of power supplied" is the amount of power supplied by the
power supply apparatus 10 indicated in the corresponding record.

[0157] "Power supply apparatus ID" is an ID for uniquely identifying the
power supply apparatus 10 indicated in the corresponding record that has
supplied power.

[0158] "Record registration time" is a time at which the corresponding
record has been registered.

[0159] A record in the surplus power use information table T30 illustrated
in FIG. 7 indicates that a power of 500 Wh associated with the power ID
of "1504011040766" has been supplied by a power supply apparatus 10 whose
power supply apparatus ID is "abcde98765" in "04/01/2015 10:45:00 to
10:50:00". The record has been registered at "04/01/2015 10:50:00".

[0160] FIG. 8 is a diagram illustrating a power information management
table T40 according to the present embodiment.

[0161] The power information management table T40 is a table held by the
power information obtaining unit 421. In the power information management
table T40, the amount of power purchased and the amount of power sold in
the home 20 of the user U1 in each time period are stored as a record.

[0162] "Contract ID" is an ID for uniquely identifying a power supply
contract in which the amount of power purchased and the amount of power
sold indicated in a corresponding record have been measured.

[0163] "Meter ID" is an ID for uniquely identifying the meters (the meter
23 and the meter 25) that have measured the amount of power purchased and
the amount of power sold indicated in the corresponding record.

[0164] "Time period start time" is a start time of a time period in which
the amount of power purchased and the amount of power sold indicated in
the corresponding record have been measured.

[0165] "Time period end time" is an end time of a time period in which the
amount of power purchased and the amount of power sold indicated in the
corresponding record have been measured.

[0166] "Amount of power purchased" is a value indicating the amount of
power purchased indicated in the corresponding record and expressed, for
example, in Wh.

[0167] "Amount of power sold" is a value indicating the amount of power
sold indicated in the corresponding record and expressed, for example, in
Wh.

[0168] A first record in the power information management table T40
illustrated in FIG. 8, for example, indicates that, in the power supply
contract whose contract ID is "00001", the meter 23 whose meter ID is
"123456789" has measured a purchased power of 0 Wh and a sold power of
1,000 Wh in a time period "04/01/2015 10:00:00 to 10:30:00".

[0169] FIG. 9 is a diagram illustrating a power supply apparatus use
information table T50 according to the present embodiment.

[0170] The power supply apparatus use information table T50 is a table
held by the surplus power use history management unit 426. In the power
supply apparatus use information table T50, the amount of surplus power
and the amount of grid power in the amount of power supplied by the power
supply apparatus 10 are stored as a record.

[0171] "Contract ID" is an ID for uniquely identifying a power supply
contract relating to the amount of surplus power supplied and the amount
of grid power supplied indicated in a corresponding record.

[0172] "Power supply apparatus ID" is an ID for uniquely identifying the
power supply apparatus 10 that has performed power supply relating to the
corresponding record.

[0173] "Power supply period start time" is a start time of a period in
which the power supply relating to the corresponding record has been
performed.

[0174] "Power supply period end time" is an end time of the period in
which the power supply relating to the corresponding record has been
performed.

[0175] "Amount of power supplied" is a value indicating the amount of
power supplied relating to the record and expressed, for example, in Wh.

[0176] "Amount of surplus power supplied" is a value indicating the amount
of surplus power in the amount of power supplied relating to the
corresponding record and expressed, in Wh.

[0177] "Amount of grid power supplied" is a value indicating the amount of
grid power in the amount of power supplied relating to the corresponding
record and expressed, in Wh.

[0178] A first record in the power supply apparatus use information table
T50 illustrated in FIG. 9, for example, indicates that, in the power
supply contract whose contract ID is "00001", the power supply apparatus
10 whose power supply apparatus ID is "abcde98765" supplies a power of
500 Wh. In this power, the amount of surplus power supplied is 500 Wh,
and the amount of grid power supplied is 0 Wh.

[0179] Next, the method for identifying surplus power, a method for
inquiring about the possibility of power supply, and a method for
responding to an inquiry will be described.

[0180] FIG. 10 is a diagram illustrating surplus power according to the
present embodiment. FIG. 10 is a diagram illustrating the method for
identifying surplus power used by the power management apparatus 41.

[0181] FIG. 10 illustrates changes in the amount of surplus power, which
is the amount of power generated by the power generation apparatus 21 and
supplied to the transmission and distribution network 50, over time. A
"time period" illustrated in FIG. 10 refers to a unit time in which the
retailer 40 needs to achieve balancing between supply and demand of
power. That is, the retailer 40 controls power supply-demand balance such
that supply and demand match in the time period. A time period x
illustrated in FIG. 10 is a period from a time T(x) to a time T(x+1).

[0182] The power management apparatus 41 obtains the amount of surplus
power 301 illustrated in FIG. 10 by obtaining the amount of power
measured by the meter 23, that is, the amount of power flowing from the
home 20 of the user U1 to the transmission and distribution network 50.
FIG. 10 illustrates a case in which, when the power management apparatus
41 obtains the amount of power from the meter 23, the meter 23 has
obtained and held the amount of power before a time T(x)+t.

[0183] The power management apparatus 41 sums the amount of surplus power
301 obtained from the meter 23 to identify the amount of surplus power
EP1 in the time period x.

[0184] The power management apparatus 41 may identify the expected amount
of surplus power 302 in a part of the time period x after the time T(x)+t
as well as the amount of surplus power 301 obtained from the meter 23. In
this case, the power management apparatus 41 may identify the amount of
surplus power EP2 in the time period x by summing the amount of surplus
power 301 and the amount of surplus power 302. In doing so, the amount of
surplus power caused in the time period x can be used more efficiently in
the power management system 1.

[0185] FIG. 11 is a diagram illustrating an inquiry about the possibility
of power supply and a response to the inquiry according to the present
embodiment. FIG. 11 illustrates the amount of surplus power identified by
the surplus power identification unit 422 after an inquiry about the
possibility of power supply is made in a time period y.

[0186] If the communication terminal 31 inquires of the power management
apparatus 41 about the possibility of power supply at 10:17, the surplus
power identification unit 422 identifies the amount of surplus power as
800 Wh by accumulating the amount of power (340 Wh, 426 Wh, and 34 Wh) in
measurement periods from 10:30 to 10:45 that have already been obtained
by the power information obtaining unit 421. The surplus power
identification unit 422 then transmits a value indicating the amount of
surplus power to the communication terminal 31 as a response.

[0187] When identifying surplus power, the surplus power identification
unit 422 may estimate the amount of surplus power in measurement periods
in the time period y from which the amount of surplus power has not yet
been obtained and add an accumulated value of the estimated amount of
surplus power to the aforementioned amount of surplus power. More
specifically, the surplus power identification unit 422 may identify the
amount of surplus power in the time period y as 1,600 Wh, for example, by
estimating that the amount of surplus power in measurement periods from
10:45 to 11:00 is the same as that in the time periods from 10:30 to
10:45.

[0188] Next, a process performed by the power management system 1 will be
described.

[0189] FIG. 12 is a flowchart illustrating an overall process performed by
the power management system 1 according to the present embodiment.

[0190] The power management system 1 performs processing in steps S11 to
S14 for each time period (loop A).

[0191] In steps S11 to S14, the power management system 1 performs the
process for inquiring about the possibility of power supply, the process
for identifying surplus power, the process for requesting power supply,
and the process for reporting power supply.

[0192] The power management system 1 also performs a settlement process in
a cycle independent of the above processes performed in each time period
(step S15). The cycle may have any length insofar as the cycle is longer
than each time period. The length of the cycle may be, for example, a
month.

[0193] Details of processing in the above steps will be described
hereinafter.

[0194] FIG. 13 is a sequence diagram illustrating transmission of
information in the power management system 1 according to the present
embodiment from the inquiry about the possibility of power supply to the
power supply report. The process performed by the power management system
1 will be described in more detail with reference to FIG. 13.

[0195] Steps illustrated in FIG. 13 are included in the processing steps
illustrated in FIG. 12. Step S101 illustrated in FIG. 13, for example, is
processing included in step S11 illustrated in FIG. 12, and steps S102 to
S105 illustrated in FIG. 13 are processing included in step S12
illustrated in FIG. 12. Steps S111 to S114 illustrated in FIG. 13 are
processing included in step S13 illustrated in FIG. 12, and step S115
illustrated in FIG. 13 is processing included in step S14 illustrated in
FIG. 12. This, however, is an example, and relationships between steps
are not limited to this.

[0196] In step S101, the communication terminal 31 of the user U1
transmits an inquiry about the possibility of power supply to the power
management apparatus 41. The power management apparatus 41 receives the
inquiry about the possibility of power supply. The inquiry about the
possibility of power supply is used for inquiring of the power management
apparatus 41 whether the power supply apparatus 10 in the power
management system 1 can supply power, that is, whether the home 20 of the
user U1 causes surplus power. When inquiring about the possibility of
power supply, the communication terminal 31 transmits a contract ID,
which is an ID for uniquely identifying a contract between the user U1
and the retailer 40. Alternatively, the communication terminal 31 may
transmit a user ID, which is an ID for uniquely identifying the user U1,
instead of the contract ID, while associating the user ID with the
inquiry about the possibility of power supply. The user ID of the user U1
will also be referred to as "first user identification information".

[0197] The communication terminal 31 transmits the inquiry about the
possibility of power supply to the power management apparatus 41 using a
communication path through a communication line. Alternatively, the
inquiry about the possibility of power supply may be automatically
transmitted, for example, after a certain application is activated on a
smartphone, which is the communication terminal 31, or after the user U1
performs a certain operation.

[0198] In step S102, the power management apparatus 41 transmits an
inquiry about the amount of surplus power to the meter 23 of the home 20
of the user U1. The power management apparatus 41 requests the meter 23
to output a value indicating the amount of surplus power corresponding to
a time period including a reception time, which is a time at which the
inquiry about the possibility of power supply in step S101 has been
received (input). More specifically, the power management apparatus 41
identifies the user U1 by referring to the contract ID included in the
inquiry about the possibility of power supply in step S101. The power
management apparatus 41 then transmits the inquiry about the amount of
surplus power to request the meter 23 of the home 20 of the identified
user U1 to transmit the value indicating the amount of surplus power
measured by the meter 23 thereto. Alternatively, the power management
apparatus 41 may include information for identifying a period of the
amount of surplus power to be obtained in the inquiry about the amount of
surplus power and transmit the inquiry.

[0199] In step S103, the meter 23 transmits the value indicating the
amount of surplus power to the power management apparatus 41 in
accordance with the inquiry about the amount of surplus power received
from the power management apparatus 41 in step S102. The power management
apparatus 41 receives the amount of surplus power transmitted from the
meter 23. The meter 23 may transmit individual values (340 Wh, 426 Wh,
and 34 Wh in the example illustrated in FIG. 11) indicating the amount of
surplus power in measurement periods in the time period including a
current time or may transmit an accumulated value (800 Wh in the example
illustrated in FIG. 11) of the amount of surplus power in the measurement
periods in the time period including the current time. In the following
description, the former will be taken as an example. If a period is
specified in step S102, the meter 23 transmits a value indicating the
amount of surplus power in the period identified by the information to
the power management apparatus 41. The power management apparatus 41
stores the received values indicating the amount of surplus power in the
surplus power information table T10.

[0200] In step S104, the power management apparatus 41 identifies surplus
power on the basis of the amount of surplus power obtained in step S103.
The power management apparatus 41 issues a power ID, which is an ID for
uniquely identifying the surplus power, and gives the power ID to the
identified surplus power. In other words, the power management apparatus
41 identifies the surplus power on the basis of the amount of surplus
power obtained in step S103 and issues the power ID, which is the ID for
uniquely identifying the surplus power, while associating the power ID
with the surplus power. More specifically, the power management apparatus
41 identifies the surplus power by calculating an accumulated value of
the amount of surplus power in the measurement periods obtained in step
S103. The identification of the surplus power and the provision of the
power ID in this step are performed in accordance with the inquiry about
the possibility of power supply in step S101. The power ID is information
for validating power supply performed by the power supply apparatus 10
using the surplus power corresponding to the time period including the
current time.

[0201] In step S105, the power management apparatus 41 transmits, to the
communication terminal 31, the power ID given in step S104. When
transmitting the power ID, the power management apparatus 41 notifies the
communication terminal 31 of the amount of power available. The amount of
power available is the same as the amount of surplus power identified in
step S104 and indicates the amount of power that can be supplied from the
power supply apparatus 10 using the power ID. Instead of transmitting the
power ID to the communication terminal 31, the power management apparatus
41 may let the user U1 obtain the power ID in a manner that a person can
understand the power ID. The user U1 may, for example, obtain a paper
medium on which the power ID is written, or the user U1 may hear the
power ID as a speech sound.

[0202] In step S105, the power management apparatus 41 may determine
whether or not the accumulated value of the amount of surplus power
corresponding to the time period is equal to or smaller than a certain
minimum value. If the accumulated value of the amount of surplus power
corresponding to the time period is equal to or smaller than the certain
minimum value, the power management apparatus 41 may perform control such
that the power ID is not issued or associated with the accumulated value
of the amount of surplus power corresponding to the time period. In this
case, the power management apparatus 41 may perform control such that the
power ID and the accumulated value are not transmitted to the
communication terminal 31 in accordance with the inquiry of the
possibility of power supply. In addition, in this case, the power
management apparatus 41 may perform control in such a way as to notify
the communication terminal 31 that the accumulated value of the amount of
surplus power corresponding to the time period is equal to or smaller
than the certain minimum value in accordance with the inquiry of the
possibility of power supply. In doing so, if the amount of power that can
be supplied from the power supply apparatus 10 is equal to or smaller
than the certain minimum value, the power management apparatus 41 can
prohibit the power supply apparatus 10 from supplying power or notify the
user U1 of the prohibition.

[0203] In step S111, the communication terminal 31 sends a power supply
request to the power supply apparatus 10. The power supply request is
information indicating that the user U1 desires to receive power with the
load apparatus 32. The power supply request includes the power ID
transmitted from the power management apparatus 41 in step S105 and the
amount of power to be used, which is the amount of power that the user U1
desires to receive. The power supply apparatus 10 receives the power
supply request and the power ID included in the power supply request.
Although the communication terminal 31 inputs the power supply request to
the power supply apparatus 10 in the above description, another apparatus
may input the power supply request to the power supply apparatus 10,
instead. The amount of power to be used may be a value equal to or
smaller than the amount of power available associated with the power ID,
or may be a sign indicating the amount of power available.

[0204] The power supply request is transmitted, for example, by bringing
the communication terminal 31 close to the near field communication port
that is the input interface 11 of the power supply apparatus 10 and
performing near field communication. Alternatively, the power supply
request may be transmitted through a communication line. Alternatively,
the user U1 may manually input the power ID using the keys that are the
input interface 11 in order to transmit the power supply request.

[0205] In step S112, the power supply apparatus 10 inquires of the power
management apparatus 41 about the power ID obtained as a result of the
power supply request transmitted in step S111. More specifically, the
power supply apparatus 10 inquires of the power management apparatus 41
whether the power ID is a legitimate, valid power ID that has been issued
by the power management apparatus 41. If the power ID has been forged or
is a copy of a power ID that has already been used in the past, for
example, it can be determined that the power ID is not legitimate or, if
the power ID corresponds to the amount of surplus power in a past time
period, not valid.

[0206] In the inquiry in step S112, the power supply apparatus 10 may also
inquires of the power management apparatus 41 about the amount of power
to be used transmitted from the communication terminal 31 in step S105.
If the amount of power to be used exceeds the amount of power available
corresponding to the power ID, it can be determined that the amount of
power to be used is not reasonable.

[0207] In step S113, the power management apparatus 41 transmits, to the
power supply apparatus 10, a result of the inquiry about the power ID
transmitted in step S112. More specifically, if the power ID transmitted
in step S112 is legitimate, the power management apparatus 41 transmits a
response indicating that the power ID is legitimate.

[0208] In step S114, the power supply apparatus 10 supplies the amount of
power to be used received along with the power ID in the power supply
request to the load apparatus 32 connected thereto. At this time, the
power supply apparatus 10 does not receive money corresponding to the
amount of power supplied, that is, prohibits the reception of money. In
other words, the power supply apparatus 10 supplies power that does not
cause a charging process to the load apparatus 32. If, as described
above, the power supply apparatus 10 has supplied power to the load
apparatus 32 on the basis of a single power ID, the power supply
apparatus 10 may be prevented from supplying power to the load apparatus
32 again on the basis of the power ID. If the amount of power to be used
is smaller than the amount of power available, the power supply apparatus
10 may supply power again in the same time period on the basis of the
power ID insofar as the sum of the amount of power supplied using the
power ID is equal to or smaller than the amount of power available.

[0209] In step S115, if the power supply apparatus 10 has supplied power
to the load apparatus 32 in step S114, the power supply apparatus 10
transmits a power supply report to the power management apparatus 41. The
power supply report includes the power ID and the amount of power
supplied.

[0210] Although the meter 23 transmits a value indicating the amount of
surplus power in accordance with the inquiry about the amount of surplus
power in the above description, the meter 23 may periodically transmit a
value indicating the amount of surplus power, instead. That is, the
processing in steps S101 to S105 illustrated in FIG. 13 may be replaced
by processing illustrated in FIG. 14.

[0211] FIG. 14 is a sequence diagram illustrating transmission of
information in the power management system 1 according to a modification
of the present embodiment from the process for inquiring about the
possibility of power supply to the process for reporting power supply.

[0212] In step S103A, the meter 23 periodically transmits a value
indicating the amount of surplus power to the power management apparatus
41 in each measurement period. The power management apparatus 41
periodically receives the value indicating the amount of surplus power.
The power management apparatus 41 stores the received value indicating
the amount of surplus power in the surplus power information table T10.
Step S103A is different from step S103 in that the meter 23 automatically
transmits the value indicating the amount of surplus power in step S103A.

[0213] In step S101A, the communication terminal 31 of the user U1
transmits an inquiry about the possibility of power supply to the power
management apparatus 41.

[0214] In step S104A, the power management apparatus 41 identifies surplus
power on the basis of the amount of surplus power obtained in step S103A.
The power management apparatus 41 then issues a power ID, which is an ID
for uniquely identifying the surplus power, and gives the power ID to the
identified amount of surplus power. More specifically, if the power
management apparatus 41 receives the inquiry about the possibility of
power supply in step S101A, the power management apparatus 41 accumulates
values of the amount of surplus power corresponding to a period from a
start time of a time period including a reception time, which is a time
at which the inquiry about the possibility of power supply has been
received, to the reception time. The power management apparatus 41 then
generates an accumulated value of the amount of surplus power
corresponding to the time period to identify the surplus power.

[0215] Step S105 is the same as step S105 illustrated in FIG. 13.

[0216] FIG. 15 is a sequence diagram illustrating transmission of
information in the power management system 1 according to the present
embodiment during the charging process. The process performed by the
power management system 1 will be described in more details with
reference to FIG. 15.

[0217] Steps illustrated in FIG. 15 are included in the processing steps
illustrated in FIG. 12. Steps S122 to S124 illustrated in FIG. 15, for
example, are included in step S15 illustrated in FIG. 12. This, however,
is an example, and relationships between steps are not limited to this.

[0218] In step S122, the power management apparatus 41 performs the
settlement process. In the settlement process, a price obtained by
subtracting money (a price) corresponding to the amount of surplus power
supplied from the home 20 of the user U1 from a price corresponding to
the amount of power supplied to the load apparatus 22 from the
transmission and distribution network 50 and consumed is calculated as a
bill to be sent to the user U1 on the basis of the power supply contract
between the retailer 40 and the user U1. At this time, the price is
calculated while subtracting the amount of power supplied from the power
supply apparatus 10 in step S114 from the amount of surplus power
supplied from the home 20 of the user U1.

[0219] In step S123, the retailer 40 sends the bill (electricity bill)
calculated in the settlement process in step S122 to the user U1.

[0220] In step S124, the user U1 pays the electricity bill sent thereto in
step S123.

[0221] Steps S112 and S113 need not necessarily be performed if it is
clear that the power supply apparatus 10 holds a legitimate power ID.

[0222] The charging process in step S122 and the sending of a bill in step
S123 are performed in each period specified in the power supply contract
between the retailer 40 and the user U1. The charging process is
performed, for example, each month.

[0223] Details of processes performed by the function blocks of the power
management apparatus 41 will be described hereinafter.

[0224] In step S11 illustrated in FIG. 12, the communication terminal 31
only inquires of the power management apparatus 41 about the possibility
of power supply, and description of details of this processing is
omitted.

[0225] FIG. 16 is a flowchart illustrating the process performed by the
power management apparatus 41 according to the present embodiment. The
flowchart of FIG. 16 illustrates the process performed by the power
management apparatus 41 in step S12 illustrated in FIG. 12.

[0226] In step S601, the surplus power identification unit 422 identifies
the amount of surplus power. Step S601 corresponds to step S104 (FIG. 13)
or step S104A (FIG. 14). The processing in step S601 will be described in
detail later.

[0227] In step S602, the surplus power identification unit 422 determines
whether or not the amount of surplus power identified in step S601 is
equal to or larger than a certain value. If the surplus power
identification unit 422 determines that the amount of surplus power is
equal to or larger than the certain value, the process proceeds to step
S603. On the other hand, if the surplus power identification unit 422
determines that the amount of surplus power is not equal to or larger
than the certain value (that is, smaller than the certain value), the
process proceeds to step S605.

[0228] In step S603, the power ID management unit 424 gives a power ID to
surplus power corresponding to the amount of surplus power identified in
step S601. Step S603 corresponds to step S104 (FIG. 13) or step S104A
(FIG. 14).

[0229] In step S604, the power ID management unit 424 transmits, to the
communication terminal 31, the power ID given in step S603. The power ID
management unit 424 also transmits a value indicating the amount of
surplus power identified in step S601 to the communication terminal 31 as
the amount of power available. The amount of power available is a value
indicating the amount of power available at a time when the power supply
apparatus 10 supplies the surplus power.

[0230] In step S605, the surplus power identification unit 422 notifies
the communication terminal 31 that power cannot be supplied (power supply
is impossible).

[0231] As a result of the above process, the power management apparatus 41
appropriately transmits the power ID in response to the inquiry about the
possibility of power supply from the communication terminal 31.

[0232] FIG. 17 is a first flowchart illustrating the process for
identifying surplus power performed by the surplus power identification
unit 422 according to the present embodiment. This flowchart illustrates
details of the processing in step S601 illustrated in FIG. 16 and is true
in a case in which the meter 23 periodically transmits the value
indicating the amount of surplus power to the power management apparatus
41 as illustrated in FIG. 14.

[0233] In step S701, the surplus power identification unit 422 obtains the
current time. A time period including the current time will be referred
to as the "time period x", and the start time of the time period x will
be denoted by T(x). In this case, the current time is expressed as
T(x)+t. Here, t corresponds to time elapsed since T(x) until the current
time.

[0234] In step S702, the start time T(x) of the time period including the
current time is identified on the basis of the current time T(x)+t
obtained in step S701.

[0235] In step S703, the surplus power identification unit 422 calculates,
in the surplus power stored in the surplus power information table T10,
the total amount of surplus power, that is, an accumulated value of the
amount of surplus power, of a consumer corresponding to the contract ID
from the time T(x) to a time up to which the amount of surplus power has
already been obtained in the time period x.

[0236] As a result of the above process, the power management apparatus 41
can identify the surplus power.

[0237] The process illustrated in FIG. 17 may be replaced by a process
illustrated in FIG. 18.

[0238] FIG. 18 is a second flowchart illustrating the process for
identifying surplus power performed by the power management apparatus 41
according to the present embodiment. This flowchart illustrates details
of the processing in step S601 illustrated in FIG. 16 and is true in a
case in which the meter 23 transmits the amount of surplus power to the
meter 23 in accordance with an inquiry about the amount of surplus power
as illustrated in FIG. 13.

[0239] Steps S801 and S802 are the same as steps S701 and S702,
respectively, illustrated in FIG. 17.

[0240] In step S803, the surplus power identification unit 422 requests
the meter 23 of the consumer corresponding to the contract ID to transmit
data regarding the amount of surplus power after the start time T(x) of
the time period including the current time. The surplus power
identification unit 422 then obtains the data regarding the amount of
surplus power in each measurement period after the time T(x).

[0241] In step S804, the surplus power identification unit 422 stores the
obtained data regarding the amount of surplus power in the surplus power
information table T10. The surplus power identification unit 422 then
calculates, in the amount of surplus power stored in the surplus power
information table T10, the total amount of surplus power, that is, an
accumulated value of the amount of surplus power, of the consumer
corresponding to the contract ID from the time T(x) to the current time.

[0242] FIG. 19 is a flowchart illustrating the process for inquiring about
a power ID performed by the power management apparatus 41 according to
the present embodiment. The flowchart of FIG. 19 illustrates the
processing performed by the power management apparatus 41 in step S13
illustrated in FIG. 12.

[0243] In step S901, the power supply possibility determination unit 425
of the power management apparatus 41 receives an inquiry about a power ID
from the power supply apparatus 10 through the communication unit 423.
The received inquiry about a power ID includes a power ID and the amount
of power to be supplied from the power supply apparatus 10. The inquiry
about a power ID is transmitted from the power supply apparatus 10 (step
S112 illustrated in FIG. 13).

[0244] In step S902, the power supply possibility determination unit 425
determines whether the power ID included in the inquiry about the power
ID received in step S901 exists in the power ID management table T20. If
the power ID exists, the process proceeds to step S904. On the other
hand, if the power ID does not exist, the process proceeds to step S903.

[0245] In step S903, the power supply possibility determination unit 425
transmits "invalid: illegitimate power ID" through the communication unit
423 as an inquiry result (corresponds to step S113 illustrated in FIG.
13). The inquiry result "invalid: illegitimate power ID" indicates that
because the power ID received in step S901 is illegitimate, the power
supply apparatus 10 cannot supply power using the power ID. The power
supply apparatus 10 is therefore prohibited from supplying power using
the power ID.

[0246] In step S904, the power supply possibility determination unit 425
determines whether the expiration time of the power ID has come. If the
expiration time of the power ID has not come, the process proceeds to
step S906. On the other hand, if the expiration time of the power ID has
come (that is, the power ID has expired), the process proceeds to step
S905.

[0247] In step S905, the power supply possibility determination unit 425
transmits "invalid: power ID has expired" through the communication unit
423 as the inquiry result (corresponds to step S113 illustrated in FIG.
13). The inquiry result "invalid: power ID has expired" indicates that
because the power ID received in step S901 has expired, the power supply
apparatus 10 cannot supply power using the power ID. The power supply
apparatus 10 is therefore prohibited from supplying power using the power
ID.

[0248] In step S906, the power supply possibility determination unit 425
determines whether or not the amount of power included in the inquiry
about the power ID received in step S901 is equal to or smaller than the
amount of power available corresponding to the power ID included in the
inquiry about a power ID. The amount of power available corresponding to
the power ID is managed in the power ID management table T20. If the
amount of power is equal to or smaller than the amount of power
available, the process proceeds to step S908. On the other hand, if the
amount of power is not equal to or smaller than the amount of power
available, the process proceeds to step S907.

[0249] In step S907, the power supply possibility determination unit 425
transmits "invalid: excessive amount of power" through the communication
unit 423 as the inquiry result (corresponds to step S113 illustrated in
FIG. 13). The inquiry result "invalid: excessive amount of power"
indicates that because the amount of power included in the inquiry about
a power ID exceeds the amount of power that can be supplied from the
power supply apparatus 10 using the power ID included in the inquiry
about a power ID received in step S901, the power supply apparatus 10
cannot supply power using the power ID. The power supply apparatus 10 is
therefore prohibited from supplying power using the power ID.

[0250] In step S907, the power supply possibility determination unit 425
may transmit "valid: within amount of power available" through the
communication unit 423 as the inquiry result (not illustrated). The
inquiry result "valid: within amount of power available" indicates that
the power supply apparatus 10 may supply an amount of power that can be
supplied from the power supply apparatus 10 using the power ID included
in the inquiry about a power ID received in step S901 (that is, power
that does not cause a charging process) and that is equal to or smaller
than the amount of power available.

[0251] In step S908, the power supply possibility determination unit 425
transmits "valid" through the communication unit 423 as the inquiry
result (corresponds to step S113 illustrated in FIG. 13). The inquiry
result "valid" indicates that the power supply apparatus 10 can supply
power using the power ID included in the inquiry about a power ID
received in step S901.

[0252] As a result of the above process, the power management apparatus 41
can appropriately respond to the inquiry about the power ID from the
power supply apparatus 10.

[0253] FIG. 20 is a flowchart illustrating the process for updating the
amount of surplus power used performed by the power management apparatus
41 according to the present embodiment. The flowchart of FIG. 20
illustrates the processing performed by the power management apparatus 41
in step S14 illustrated in FIG. 12.

[0254] In step S1001, the surplus power use history management unit 426 of
the power management apparatus 41 receives a power supply report through
the communication unit 423. The power supply report includes a power ID
and the amount of power supplied by the power supply apparatus 10 using
the power ID. The power supply report is transmitted from the power
supply apparatus 10 (step S115 illustrated in FIG. 13).

[0255] In step S1002, the surplus power use history management unit 426
updates the amount of power available corresponding to the power ID by
subtracting the amount of power included in the power supply report
received in step S1001 from the amount of power available stored in the
power ID management table T20.

[0256] In step S1003, the surplus power use history management unit 426
registers the amount of power included in the power supply report
received in step S1001 to the surplus power use information table T30 as
the amount of power supplied.

[0257] As a result of the above process, the power management apparatus 41
updates various pieces of information on the basis of the received power
supply report.

[0258] FIG. 21 is a flowchart illustrating the process for calculating an
electricity bill in the settlement process according to the present
embodiment.

[0259] In step S1101, the settlement process unit 427 of the power
management apparatus 41 calculates a price A corresponding to the amount
of power purchased a in the home 20 of the user U1. The amount of power
purchased a is obtained from the amount of power indicated by the meter
25, that is, the amount of power purchased a is an accumulated value of
the amount of power purchased stored in the power information management
table T40 over a certain period.

[0260] In step S1102, the settlement process unit 427 calculates the
amount of power sold b. The amount of power sold b is obtained from the
amount of power indicated by the meter 23, that is, the amount of power
sold b is an accumulated value of the amount of power sold stored in the
power information management table T40 over the certain period.

[0261] In step S1103, the settlement process unit 427 calculates the
amount of surplus power used c. The amount of surplus power used c is, in
the surplus power, the amount of power supplied from the power supply
apparatus 10, that is, the amount of surplus power used c is an
accumulated value of the amount of surplus power supplied stored in the
power supply apparatus use information table T50 over the certain period.

[0262] In step S1104, the settlement process unit 427 calculates a price D
corresponding to the amount of power purchased d from the power supply
apparatus 10. The amount of power purchased d indicates the amount of
grid power supplied from the power supply apparatus 10, that is, the
amount of power purchased d is an accumulated value of the amount of grid
power supplied stored in the power supply apparatus use information table
T50 over the certain period.

[0263] In step S1105, the settlement process unit 427 calculates an
electricity bill using the following expression 1 on the basis of the
prices A and D, the amount of power sold b, and the amount of surplus
power used c calculated in steps S1101 to S1104.

[0265] As a result of the above process, the power management apparatus 41
settles the electricity bill after calculating the electricity bill for
the user U1.

[0266] As described above, in the power management system 1 according to
the present embodiment, surplus power caused in a home of a user
(consumer) is supplied to the power system (reverse flow) whereas the
user can receive power from the power system at a place different from
the user's home. As a result, the user can not only sell the surplus
power but also receive power corresponding to the surplus power at
another place. The power management system 1 can thus make wider use of
surplus power.

Second Embodiment

[0267] In a second embodiment, a power management system will be described
capable of making wider use of surplus power caused in a user's home by
consuming the surplus power for a person different from the user at a
place different from the user's home. In the following description, the
user will be referred to as a "user U1", and the person different from
the user will be referred to as a "user U2".

[0268] In the present embodiment, the same components as those according
to the first embodiment are given the same reference numerals, and
detailed description thereof is omitted.

[0269] First, a case in which the power management system according to the
present embodiment manages power will be described while taking an
example. The power management performed by the power management system
according to the present embodiment, however, is not limited to this
example.

[0270] Both the user U1 and the user U2 use a social networking service
(SNS) sites on the Internet. A power generation apparatus is installed in
the home 20 of the user U1 and is generating power. The user U2 is on
his/her travels and driving an EV. When the user U1 likes content posted
on the SNS site by the user U2 during the travel, the user U1 desires to
provide surplus power caused in the home thereof for the user U2. The
user U2 stops at a rest area in which a power supply apparatus is
installed and charges the EV. The power management system performs
management such that the surplus power caused in the home 20 of the user
U1 offsets the power supplied to the EV of the user U2 from the power
supply apparatus. The power management system that manages power in this
manner will be specifically described hereinafter.

[0271] FIG. 22 is an overview of the configuration of a power management
system according to the present embodiment. FIG. 23 is a block diagram
illustrating the configuration of the power management system 2 according
to the present embodiment. The power management system 2 will be
described with reference to these drawings.

[0272] In the power management system 2, there are two users, namely the
user U1 and the user U2. The power management system 2 is different from
the power management system 1 according to the first embodiment in that
the user (user U1) who owns a power generation apparatus at home and the
user (user U2) who receives power from a power supply apparatus are
different from each other.

[0273] The power generation apparatus 21, the load apparatus 22, and the
meter 23 are installed in the home 20 of the user U1. The user U1 owns
the communication terminal 31. The user U1 may stay at the home 20
thereof, or may stay outside the home 20.

[0274] The user U2 stays near the power supply apparatus 10. The user U2
owns a communication terminal 35 and a load apparatus 36. The
communication terminal 35 and the load apparatus 36 have the same
functions as the communication terminal 31 and the load apparatus 32,
respectively, according to the first embodiment.

[0275] FIG. 24 is a first sequence diagram illustrating transmission of
information in the power management system 2 according to the present
embodiment. A process performed by the power management system 2 will be
described with reference to FIG. 24. Detailed description of the same
processing steps as those for the power management system 1 according to
the first embodiment is omitted.

[0276] In steps S101 to S105, the communication terminal 31 inquires about
the possibility of power supply and receives a power ID.

[0277] In step S206, the communication terminal 31 transmits the power ID
to the communication terminal 35. The power ID transmitted here is one
given to the surplus power caused in the home 20 of the user U1. Since
the communication terminal 31 transmits the power ID to the communication
terminal 35, the user U2 can use the surplus power caused in the home 20
of the user U1.

[0278] After the communication terminal 31 transmits the power ID to the
communication terminal 35, the power ID held by the communication
terminal 31 may be deleted. In doing so, the communication terminal 31
(user U1) can be prohibited from supplying power to the load apparatus 22
from the power supply apparatus 10 using the power ID. That is, the power
ID can be appropriately transferred or moved from the user U1 to the user
U2.

[0279] When transmitting the power ID to the communication terminal 35,
the communication terminal 31 may generate a new power ID (also referred
to as a "second power ID" or "second identification information")
associated with the power ID (also referred to as a "first power ID") and
transmit the generated second power ID to the communication terminal 35.
In this case, the power management apparatus 41 invalidates the first
power ID. In doing so, the communication terminal 35 (user U2) is allowed
to supply power to the load apparatus 36 using the second power ID,
whereas the communication terminal 31 (user U1) is prohibited from
supplying power to the load apparatus 22. In this method, too, the power
ID can be appropriately transferred or moved from the user U1 to the user
U2.

[0280] In step S211, the communication terminal 35 transmits a power
supply request to the power supply apparatus 10. The power supply request
includes the power ID transmitted from the communication terminal 31 in
step S206 and the amount of power to be used, which is the amount of
power that the user U2 desires to receive.

[0281] In steps S112 and S113, an inquiry about the power ID obtained from
the power supply request in step S211 is made.

[0282] In step S214, the power supply apparatus 10 supplies power to the
load apparatus 36 connected thereto.

[0283] Although the communication terminal 31 transmits the power ID to
the communication terminal 35 in step S206 after the power management
apparatus 41 transmits the power ID to the communication terminal 31 in
step S105 in the above description, the power management apparatus 41 may
transmit the power ID to the communication terminal 35, instead. In doing
so, the communication terminal 35 can obtain the power ID without using
the communication terminal 31, which increases usability.

[0284] As described above, according to the power management system 2, if
the communication terminal 31 transmits a power ID and an accumulated
value of the amount of surplus power to the communication terminal 35,
which is used by the user U2, and the communication terminal 35
transmits, to the power supply apparatus 10, a second power supply
request indicating that the user U2 desires to receive power with the
load apparatus 36, which is used by the user U2 and different from the
load apparatus 32, the power supply apparatus 10 supplies an amount of
first power equal to or smaller than the amount of surplus power to the
load apparatus 36 as power that does not cause a charging process.

[0285] If the first power ID and the temporary second power ID, which is
different from the first power ID, are issued and associated with an
accumulated value of the amount of surplus power in a time period in
accordance with the inquiry about the possibility of power supply, the
first power ID, the second power ID, and the accumulated value of the
amount of surplus power in the time period are transmitted to the
communication terminal 31, the communication terminal 31 transmits the
second power ID and the accumulated value of the amount of surplus power
to the communication terminal 35 used by the user U2, the communication
terminal 35 transmits, to the power supply apparatus 10, a second power
supply request indicating that the user U2 desires to receive power with
the load apparatus 36, which is used by the user U2 and different from
the load apparatus 32, and the power supply apparatus 10 supplies an
amount of first power equal to or smaller than the amount of surplus
power to the load apparatus 36 as power that does not cause a charging
process, the first power is prohibited from being supplied to the load
apparatus 32.

[0286] As a result, it is possible to make wider use of surplus power
caused in a home of a user by consuming the surplus power for a person
different from the user at a place different from the user's home.

Third Embodiment

[0287] In a third embodiment, a power management system will be described
capable of making wider use of surplus power by consuming surplus power
that will be caused in a user's home in the future for a person different
from the user at a place different from the user's home.

[0288] In the present embodiment, the same components as those according
to the first or second embodiment are given the same reference numerals,
and detailed description thereof is omitted.

[0289] First, a case in which the power management system according to the
present embodiment manages power will be described while taking an
example. Power management performed by the power management system
according to the present embodiment, however, is not limited to this
example.

[0290] Although the surplus power caused in the home 20 of the user U1 is
provided for the user U2 in the second embodiment, the user U1 desires to
provide surplus power that will be caused in the home 20 of the user U1
in the future for the user U1 in the present embodiment.

[0291] The user U2 stops at a rest area in which a power supply apparatus
is installed and charges the EV. The power management system performs
management such that the surplus power caused in the home 20 of the user
U1 in a time period in which the EV is charged offsets the power supplied
to the EV of the user U2 from the power supply apparatus. The power
management system that manages power in this manner will be specifically
described hereinafter.

[0292] The configuration of the power management system according to the
present embodiment is the same as that of the power management system 2
according to the second embodiment.

[0293] FIG. 25 is a first sequence diagram illustrating transmission of
information in the power management system in the present embodiment. A
process performed by the power management system according to the present
embodiment will be described with reference to FIG. 25.

[0294] In step S301, the communication terminal 31 reserves a right to use
surplus power. The right to use surplus power is a right to use surplus
power that will be caused in the future. Since the user U1 reserves the
right to use surplus power using the communication terminal 31, the right
to use surplus power that will be caused by the power generation
apparatus 21 can be defined. When reserving the right to use surplus
power, the communication terminal 31 transmits a contract ID and the
amount of power requested to the power management apparatus 41. The
amount of power requested is the amount power requested to be used in the
future.

[0295] A time limit may be provided for the surplus power to be used. That
is, in the surplus power caused in the future, the user U1 may receive a
right to use only surplus power caused in a certain time period.
Alternatively, the user U1 may receive a right to use only surplus power
caused in time periods other than a certain time period. In this case,
the user U1 specifies the certain time period in step S301.

[0296] In step S302, the power management apparatus 41 gives a power ID to
reserved power. The power management apparatus 41 gives the power ID to
power corresponding to the amount of power requested included in the
reservation of the right to use surplus power received in step S301. The
power corresponding to the amount of power requested is the surplus power
that will be caused in the future.

[0297] If the certain time period is specified in step S301, the power
management apparatus 41 gives a power ID to surplus power that will be
caused in the specified certain time period or surplus power that will be
caused in the time periods other than the specified certain time period.

[0298] Alternatively, the power management apparatus 41 may reserve only
surplus power corresponding to part of the amount of power requested
specified in step S301. More specifically, the power management apparatus
41 determines whether to reserve surplus power corresponding to all the
amount of power requested specified in step S301. If the power management
apparatus 41 determines that it is difficult to reserve surplus power
corresponding to all the amount of power requested, the power management
apparatus 41 may reserve only surplus power corresponding to part of the
amount of power requested.

[0299] In step S303, the power management apparatus 41 transmits, to the
communication terminal 31, the power ID given in step S302. At this time,
the power management apparatus 41 transmits a value indicating the
reserved amount of surplus power to the communication terminal 31 as the
amount of power reserved.

[0300] In step S304, the communication terminal 31 transmits, to the
communication terminal 35 (user U2), the power ID transmitted in step
S303.

[0301] FIGS. 26 and 27 are second and third sequence diagrams illustrating
the transmission of information in the power management system according
to the present embodiment.

[0302] In step S311, the communication terminal 35 transmits a power
supply request to the power supply apparatus 10. The power supply request
includes the power ID transmitted from the communication terminal 31 in
step S304 and the amount of power to be used, which is the amount of
power that the user U2 desires to receive.

[0303] In step S312, the power supply apparatus 10 inquires of the power
management apparatus 41 about the power ID obtained as a result of power
supply request transmitted in step S311. Step S312 is the same as step
S112 in the first embodiment.

[0304] In step S313, the power management apparatus 41 transmits an
inquiry about the amount of surplus power to the meter 23 of the home 20
of the user U1.

[0305] In step S314, the meter 23 transmits the amount of surplus power to
the power management apparatus 41 in accordance with the inquiry about
the amount of surplus power received from the power management apparatus
41 in step S313.

[0306] In step S315, the power management apparatus 41 determines the
amount of actual surplus power. More specifically, the power management
apparatus 41 determines whether or not the amount of surplus power in the
time period is equal to or larger than the amount of surplus power to be
used included in the power supply request transmitted in step S311.

[0307] If the power management apparatus 41 determines in step S315 that
the amount of surplus power is equal to or larger than the amount of
power to be used (YES in step S315), processing in steps S316 and S317 is
performed. On the other hand, if the power management apparatus 41
determines in step S315 that the amount of surplus power is not equal to
or larger than the amount of power to be used (that is, if the amount of
surplus power is smaller than the amount of power to be used) (NO in step
S315), processing in steps S321 to S324 illustrated in FIG. 27 is
performed.

[0308] In step S316, the power management apparatus 41 transmits, to the
power supply apparatus 10, a result of the inquiry about the power ID
transmitted in step S312. More specifically, since the amount of surplus
power is equal to or larger than the amount of power to be used, the
power management apparatus 41 notifies the power supply apparatus 10 that
power may be supplied.

[0309] In step S317, the power supply apparatus 10 supplies power
corresponding to the amount of power to be used to the load apparatus 36
connected thereto.

[0310] In step S321, the power management apparatus 41 transmits, to the
power supply apparatus 10, a result of the inquiry about the power ID
transmitted in step S312. More specifically, since the amount of surplus
power is smaller than the amount of power to be used, the power
management apparatus 41 transmits a value indicating the amount of power
available to the power supply apparatus 10.

[0311] In step S322, the power supply apparatus 10 transmits, to the
communication terminal 35, the value indicating the amount of power
available transmitted in step S321. The communication terminal 35
displays, to the user U2, the value indicating the amount of power
available transmitted in step S322 and might receive, from the user U2,
an instruction to receive power corresponding to the amount of power
available from the power supply apparatus 10.

[0312] In step S323, the communication terminal 35 transmits the
instruction to receive power to the power supply apparatus 10. The
instruction to receive power is issued if the user U2 determines in step
S322 to receive the power corresponding to the amount of power available.

[0313] In step S324, the power supply apparatus 10 supplies the power
corresponding to the amount of power available to the load apparatus 36
connected thereto.

[0314] Although the power management apparatus 41 gives a power ID to
reserved power in step S302 in the above description, the power
management apparatus 41 may wait until the surplus power is actually
caused, instead. In this case, the power management apparatus 41 may give
a power ID to the surplus power after the surplus power is actually
caused, and transmit the power ID to the communication terminal 31. In
doing so, upon receiving the power ID in step S304, the communication
terminal 35 can instruct the power supply apparatus 10 to supply the
power to the load apparatus 36 on the basis of the actual surplus power.

[0315] Although the communication terminal 31 reserves a right to use
surplus power using the contract ID and the amount of power requested in
step S301 in the above description, the communication terminal 31 may
also use specification information for specifying the user U2. In this
case, after the surplus power is actually caused, the power management
apparatus 41 can give a power ID to the surplus power and transmit the
power ID to the communication terminal 35. In doing so, the communication
terminal 35 can obtain the power ID without using the communication
terminal 31 and instruct the power supply apparatus 10 to supply power to
the load apparatus 36 on the basis of the actual surplus power.

Modifications of Embodiments

[0316] The power management system according to each of the above
embodiments can be implemented in the following manner.

[0317] FIG. 28 is a block diagram illustrating another example of the
configuration of the power management system according to each of the
above embodiments.

[0318] A power management system 3 includes a power generation apparatus
connected to a power system, a power supply apparatus connected to the
power system, and a load apparatus connected to the power supply
apparatus. As illustrated in FIG. 28, the power management system 3
includes an identification unit 41A that identifies surplus power, which
is, in power generated by the power generation apparatus, power supplied
to the power system, a generation unit 41B that generates first
identification information associated with the surplus power, and the
power supply unit 12 that supplies an amount of first power equal to or
smaller than the amount of surplus power associated with the first
identification information from the power system to the load apparatus
through the power supply apparatus holding the first identification
information.

[0319] FIG. 29 is a flowchart illustrating a power management method
performed by the power management system according to each of the above
embodiments.

[0320] In step S1301, surplus power, which is, in the power generated by
the power generation apparatus, power supplied to the power system, is
identified.

[0321] In step S1302, the first identification information to be
associated with the surplus power is generated.

[0322] In step S1303, an amount of first power equal to or smaller than
the amount of surplus power associated with the first identification
information is supplied from the power system to the load apparatus
through the power supply apparatus holding the first identification
information.

[0323] The components in each of the above embodiments may be configured
by dedicated hardware or by executing a software program suitable for the
components. Alternatively, the components may be realized by a program
execution unit such as a central processing unit (CPU) or a processor
that reads and executes a software program recorded on a recording medium
such as a hard disk or a semiconductor memory. A software program that
realizes the power management system according to each of the above
embodiments or the like is as follows.

[0324] That is, the software program is the program stored in a
non-transitory computer-readable recording medium storing a program for
causing a computer to implement a power management method used in a power
management system including a power generation apparatus corresponding to
first user identification information, a first load apparatus used by a
user corresponding to the first user identification information, and a
power supply apparatus capable of supplying power to the first load
apparatus and installed in a place different from the power generation
apparatus. The method includes receiving, from a meter that measures the
amount of surplus power, which is, in power generated by the power
generation apparatus, power supplied from the power generation apparatus
to a power system, a surplus power value indicating the amount of surplus
power, receiving, from a first communication terminal used by the user
corresponding to the first user identification information, an inquiry
about power supply in which the surplus power is used in a first time
period that lasts a certain unit time, the inquiry being associated with
the first user identification information, issuing, in accordance with
the inquiry, first power identification information for validating power
supply performed by the power supply apparatus using the surplus power
corresponding to the first time period for an accumulated value of the
amount of surplus power corresponding to the first time period,
transmitting the first power identification information and the
accumulated value of the amount of surplus power corresponding to the
first time period to the first communication terminal, and causing the
power supply apparatus that has received a first power supply request,
which is associated with the first power identification information,
indicating that power is to be supplied to the first load apparatus to
supply an amount of first power equal to or smaller than the amount of
surplus power to the first load apparatus as power that does not cause a
charging process.

[0325] That is, the software program may be the program stored in a
computer-readable recording medium storing a program for causing a
computer to implement a power management method used in a power
management system including a power generation apparatus connected to a
power system and a power supply apparatus that is connected to the power
system and that supplies power to a load apparatus. The method includes
identifying surplus power, which is, in power generated by the power
generation apparatus, power to be supplied to the power system,
generating first identification information to be associated with the
surplus power, and supplying an amount of first power equal to or smaller
than the amount of surplus power associated with the first identification
information from the power system to the load apparatus through the power
supply apparatus that has obtained the generated first identification
information.

[0326] Part or all of the above embodiments can be described as follows,
but are not limited to the following description.

[0327] (1) A power management method used in a power management system
including a power generation apparatus connected to a power system and a
power supply apparatus that is connected to the power system and that
supplies power to a load apparatus includes identifying surplus power,
which is, in power generated by the power generation apparatus, power
supplied to the power system, generating first identification information
to be associated with the surplus power, and supplying an amount of first
power equal to or smaller than the amount of surplus power associated
with the first identification information from the power system to the
load apparatus through the power supply apparatus that has obtained the
generated first identification information.

[0328] (2) In the method according to (1), if the power supply apparatus
has not obtained the first identification information, second power that
causes a charging process may be supplied from the power system to the
load apparatus through the power supply apparatus, and if the power
supply apparatus has obtained the first identification information, the
first power that does not cause a charging process may be supplied to the
load apparatus.

[0329] (3) In the method according to (2), the power supply apparatus may
include a receiver used for paying money for the supplied power. The
method may further include receiving money using the receiver if the
second power has been supplied and not receiving money using the receiver
if the first power has been supplied.

[0330] (4) The method according to any of (1) to (3) may further include
performing, if the surplus power is supplied to the power system, a
process for providing a price corresponding to the amount of surplus
power. If the first power has been supplied, a process for providing a
price corresponding to the amount of power obtained by subtracting the
amount of first power from the amount of surplus power may be performed
in the provision process.

[0331] (5) The method according to any of (1) to (4) may further include
transmitting the first identification information to a first
communication terminal of a first user, who owns the power generation
apparatus, and, if the first communication terminal transmits, to the
power supply apparatus using the first identification information, a
request indicating that power is to be supplied from the power supply
apparatus, supplying the first power to the load apparatus.

[0332] (6) The method according to (5) may further include transmitting
the first identification information from the first communication
terminal to a second communication terminal of a second user, who is
different from the first user who owns the power generation apparatus,
and, if the second communication terminal transmits, to the power supply
apparatus using the first identification information, a request
indicating that power is to be supplied from the power supply apparatus,
supplying the first power to the load apparatus.

[0333] (7) In the method according to (6), if the first identification
information is transmitted, the first identification information held by
the first communication terminal may be deleted after the first
identification information is transmitted.

[0334] (8) The method according to (6) may further include generating, if
the first identification information is transmitted, second
identification information associated with the first identification
information but different from the first identification information,
transmitting the generated second identification information from the
first communication terminal to the second communication terminal,
supplying the first power from the power system to the load apparatus
through the power supply apparatus that has obtained the second
identification information, and prohibiting the power supply apparatus
that has obtained the first identification information from supplying the
first power.

[0335] (9) In the method according to (8), if the first identification
information is generated before the identified surplus power is actually
caused, the generated first identification information may be transmitted
to the second communication terminal after the surplus power is actually
caused.

[0336] (10) The method according to (6) may further include receiving
specification information for specifying the second user, and, if the
first identification information is generated before the identified
surplus power is actually caused, transmitting the generated first
identification information to the communication terminal of the second
user specified by the specification information after the surplus power
is actually caused.

[0337] (11) In the method according to any of (1) to (10), in the power
management system, power supply-demand balance may be adjusted in each
time period, and the power supply apparatus may supply the first power in
the same time period in which the power generation apparatus supplies the
surplus power to the power system.

[0338] (12) The method according to any of (1) to (11) may further include
measuring, in the power generated by the power generation apparatus in a
period from a start of a time period including a first time to the first
time, power supplied to the power system, identifying the measured power
as the surplus power, and supplying an amount of first power equal to or
smaller than the amount of surplus power to the load apparatus.

[0339] (13) The method according to (12) may further include identifying
power obtained by adding estimated surplus power, which is, in power
estimated to be generated by the power generation apparatus in a period
from the first time to an end of the time period, power estimated to be
supplied to the power system, to the surplus power as new surplus power,
and supplying an amount of first power equal to or smaller than the
amount of new surplus power to the load apparatus.

[0340] (14) A power management system including a power generation
apparatus connected to a power system and a power supply apparatus that
is connected to the power system and that supplies power to a load
apparatus includes an identifier that identifies surplus power, which is,
in power generated by the power generation apparatus, power supplied to
the power system, a generator that generates first identification
information to be associated with the surplus power, and a power supplier
that supplies an amount of first power equal to or smaller than the
amount of surplus power associated with the first identification
information from the power system to the load apparatus through the power
supply apparatus that has obtained the generated first identification
information.

[0341] According to (1), in the power management system, the surplus power
caused in a home of a user (consumer) is supplied to the power system
(reverse flow) whereas the power system supplies power at a place
different from the user's home. As a result, the user can not only sell
the surplus power but also receive an amount of power corresponding to
the amount of surplus power at another place. The power management system
can thus make wider use of surplus power.

[0342] According to (2), in the power management system, the user need not
pay for the power supplied from the power supply apparatus. Since the
power management system performs management such that the surplus power
offsets the power supplied from the power supply apparatus, the user need
not pay for the power supplied from the power supply apparatus. The user
can therefore make wider use of surplus power without paying extra money.

[0343] According to (3), the power management system does not receive
money corresponding to the power supplied from the power supply
apparatus. Since the power management system performs management such
that the surplus power offsets the power supplied from the power supply
apparatus, the power management system does not receive the money
corresponding to the power supplied from the power supply apparatus. The
user can therefore make wider use of surplus power without paying extra
money.

[0344] According to (4), the power management system provides, for the
user, a price corresponding to the amount of power obtained by
subtracting the amount of power supplied from the power supply apparatus
from the amount of surplus power. The user can therefore make wider use
of surplus power without paying extra money.

[0345] According to (5), the power management system supplies power to the
load apparatus after the first identification information is input to the
power supply apparatus. The user can supply power to the load apparatus
by inputting the first identification information to the power supply
apparatus. In doing so, the user can intuitively understand a time to
supply power to the load apparatus, which improves usability.

[0346] According to (6), in the power management system, the surplus power
caused in a home of a user (first user) is supplied to the power system
(reverse flow) whereas a user (second user) who does not own a power
generation apparatus can receive power from the power system. As a
result, even users who do not own a power generation apparatus can use
surplus power.

[0347] According to (7), the power management system can prohibit the
first user from making the power supply apparatus supply power to his/her
load apparatus using the first identification information after the first
user transmits the first identification information to the second user.
That is, the power management system can appropriately transfer or move
the identification information from the first user to the second user.

[0348] According to (8), in the power management system, the second user
is allowed to supply power to his/her load apparatus using the second
identification information whereas the first user is prohibited from
supplying power to his/her load apparatus. That is, the power management
system can appropriately transfer or move the identification information
from the first user to the second user.

[0349] According to (9), the communication terminal that has received the
identification information can supply power from the power supply
apparatus to the load apparatus on the basis of the actual surplus power.

[0350] According to (10), the communication terminal that has received the
identification information can obtain the identification information
without using another communication terminal and supply power from the
power supply apparatus to the load apparatus on the basis of the actual
surplus power.

[0351] According to (11), the power management system can supply power to
the load apparatus without disrupting the supply-demand balance in the
time period. As a result, it is possible to avoid increasing a power
procurement cost of a retailer.

[0352] According to (12), in the power management system, an amount of
power corresponding to the amount of surplus power actually caused in the
time period can be supplied to the load apparatus. As a result, it is
possible to avoid increasing the power procurement cost of the retailer.

[0353] According to (13), in the power management system, the sum of the
amount of surplus power actually caused in the time period and the amount
of surplus power estimated to be caused in the time period can be
supplied to the load apparatus. As a result, it is possible to avoid
increasing the power procurement cost of a retailer.

[0354] According to (14), the same advantageous effects as above can be
produced.

[0355] Although power management systems according to one or a plurality
of aspects and the like have been described on the basis of embodiments,
the present disclosure is not limited to these embodiments. The one or
plurality of aspects may include modes obtained by modifying the above
embodiments in manners that can be conceived by those skilled in the art
or modes obtained by combining components in different embodiments,
insofar as such modes do not deviate from the scope of the present
disclosure.

[0356] The present disclosure can be used for a power management system
capable of making wider use of surplus power.